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1. Tracking of an electron beam through the solar corona with LOFAR

Author

Mann, G, Breitling, F, Vocks, C, Aurass, H, Steinmetz, M, Strassmeier, KG, Bisi, MM, Fallows, RA, Gallagher, P, Kerdraon, A, Mackinnon, A, Magdalenic, J, Rucker, H, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bîrzan, L, Bonafede, A, Broderick, JW, Brüggen, M, Butcher, HR, Ciardi, B, Corstanje, A, Gasperin, FD, Geus, ED, Deller, A, Duscha, S, Eislöffel, J, Engels, D, Falcke, H, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, J, Gunst, AW, Haarlem, MV, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Hörandel, J, Horneffer, A, Juette, E, Karastergiou, A, Klijn, WFA, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Maat, P, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Rafferty, D, Reich, W, Röttgering, H, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Tagger, M, Tang, Y, Tasse, C, Veen, ST, Thoudam, S, Toribio, MC, Vermeulen, R, Weeren, RJV, Wise, MW, Wucknitz, O, Yatawatta, S, Zarka, P, Zensus, JA, Mann, G, Breitling, F, Vocks, C, Aurass, H, Steinmetz, M, Strassmeier, KG, Bisi, MM, Fallows, RA, Gallagher, P, Kerdraon, A, Mackinnon, A, Magdalenic, J, Rucker, H, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bîrzan, L, Bonafede, A, Broderick, JW, Brüggen, M, Butcher, HR, Ciardi, B, Corstanje, A, Gasperin, FD, Geus, ED, Deller, A, Duscha, S, Eislöffel, J, Engels, D, Falcke, H, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, J, Gunst, AW, Haarlem, MV, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Hörandel, J, Horneffer, A, Juette, E, Karastergiou, A, Klijn, WFA, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Maat, P, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Rafferty, D, Reich, W, Röttgering, H, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Tagger, M, Tang, Y, Tasse, C, Veen, ST, Thoudam, S, Toribio, MC, Vermeulen, R, Weeren, RJV, Wise, MW, Wucknitz, O, Yatawatta, S, Zarka, P, and Zensus, JA

Abstract

© ESO 2018. The Sun's activity leads to bursts of radio emission, among other phenomena. An example is type-III radio bursts. They occur frequently and appear as short-lived structures rapidly drifting from high to low frequencies in dynamic radio spectra. They are usually interpreted as signatures of beams of energetic electrons propagating along coronal magnetic field lines. Here we present novel interferometric LOFAR (LOw Frequency ARray) observations of three solar type-III radio bursts and their reverse bursts with high spectral, spatial, and temporal resolution. They are consistent with a propagation of the radio sources along the coronal magnetic field lines with nonuniform speed. Hence, the type-III radio bursts cannot be generated by a monoenergetic electron beam, but by an ensemble of energetic electrons with a spread distribution in velocity and energy. Additionally, the density profile along the propagation path is derived in the corona. It agrees well with three-fold coronal density model by (1961, ApJ, 133, 983).

Published
2018

2. A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations

Author

Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, and Wise, MW

Subjects
General Science & Technology, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

© 2016 Macmillan Publishers Limited. All rights reserved. Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017-1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers - cascades of secondary particles in the atmosphere - and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017-1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017-1017.5 electronvolt range.

Published
2015

3. The association of a J -burst with a solar jet

Author

Morosan, DE, Gallagher, PT, Fallows, RA, Reid, H, Mann, G, Bisi, MM, Magdalenić, J, Rucker, HO, Thidé, B, Vocks, C, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Bonafede, A, Breitling, F, Broderick, JW, Brüggen, M, Cerrigone, L, Ciardi, B, De Geus, E, Duscha, S, Eislöffel, J, Falcke, H, Garrett, MA, Grießmeier, JM, Gunst, AW, Hoeft, M, Iacobelli, M, Juette, E, Kuper, G, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Reich, W, Schwarz, DJ, Sluman, J, Smirnov, O, Steinmetz, M, Tagger, M, Ter Veen, S, Thoudam, S, Toribio, MC, Vermeulen, R, Van Weeren, RJ, Wucknitz, O, Zarka, P, Morosan, DE, Gallagher, PT, Fallows, RA, Reid, H, Mann, G, Bisi, MM, Magdalenić, J, Rucker, HO, Thidé, B, Vocks, C, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Bonafede, A, Breitling, F, Broderick, JW, Brüggen, M, Cerrigone, L, Ciardi, B, De Geus, E, Duscha, S, Eislöffel, J, Falcke, H, Garrett, MA, Grießmeier, JM, Gunst, AW, Hoeft, M, Iacobelli, M, Juette, E, Kuper, G, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Reich, W, Schwarz, DJ, Sluman, J, Smirnov, O, Steinmetz, M, Tagger, M, Ter Veen, S, Thoudam, S, Toribio, MC, Vermeulen, R, Van Weeren, RJ, Wucknitz, O, and Zarka, P

Abstract

© ESO, 2017. Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections, and numerous smaller scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles. Aims. Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena. Methods. We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet and radio data from the Low Frequency Array (LOFAR) and the Nançay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at ~11:06 UT. Results. The J-burst showed fundamental and harmonic components and was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred in the northern hemisphere at a time and location coincident with the radio burst and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet. Conclusions. Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst, which shows the path of the accelerated electrons. These electrons travelled from a region in the vicinity of the solar jet along closed magnetic field lines up to the top of a closed magnetic loop at a height of ~360 Mm. Such small-scale complex eruptive events arising from magnetic reconnection could facilitate accelerated electrons to produce continuously the large numbers of Type III

Published
2017

4. A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations

Author

Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, Wise, MW, Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, and Wise, MW

Abstract

© 2016 Macmillan Publishers Limited. All rights reserved. Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017-1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers - cascades of secondary particles in the atmosphere - and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017-1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017-1017.5 electronvolt range.

Published
2016

5. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author

Asgekar, A, Oonk, JBR, Yatawatta, S, Van Weeren, RJ, McKean, JP, White, G, Jackson, N, Anderson, J, Avruch, IM, Batejat, F, Beck, R, Bell, ME, Bell, MR, Van Bemmel, I, Bentum, MJ, Bernardi, G, Best, P, Bîrzan, L, Bonafede, A, Braun, R, Breitling, F, Van De Brink, RH, Broderick, J, Brouw, WN, Brüggen, M, Butcher, HR, Van Cappellen, W, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, De Jong, A, De Vos, M, Duscha, S, Eislöffel, J, Falcke, H, Fallows, RA, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Grit, T, Gunst, AW, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kohler, J, Kondratiev, VI, Kuniyoshi, M, Kuper, G, Law, C, Van Leeuwen, J, Maat, P, MacArio, G, Mann, G, Markoff, S, McKay-Bukowski, D, Mevius, M, Miller-Jones, JCA, Mol, JD, Morganti, R, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, H, Scheers, B, Schoenmakers, A, Sluman, J, Smirnov, O, Sobey, C, Steinmetz, M, Tagger, M, Tang, Y, Tasse, C, Vermeulen, R, Vocks, C, Wijers, RAMJ, Wise, MW, Wucknitz, O, Zarka, P, Asgekar, A, Oonk, JBR, Yatawatta, S, Van Weeren, RJ, McKean, JP, White, G, Jackson, N, Anderson, J, Avruch, IM, Batejat, F, Beck, R, Bell, ME, Bell, MR, Van Bemmel, I, Bentum, MJ, Bernardi, G, Best, P, Bîrzan, L, Bonafede, A, Braun, R, Breitling, F, Van De Brink, RH, Broderick, J, Brouw, WN, Brüggen, M, Butcher, HR, Van Cappellen, W, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, De Jong, A, De Vos, M, Duscha, S, Eislöffel, J, Falcke, H, Fallows, RA, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Grit, T, Gunst, AW, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kohler, J, Kondratiev, VI, Kuniyoshi, M, Kuper, G, Law, C, Van Leeuwen, J, Maat, P, MacArio, G, Mann, G, Markoff, S, McKay-Bukowski, D, Mevius, M, Miller-Jones, JCA, Mol, JD, Morganti, R, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, H, Scheers, B, Schoenmakers, A, Sluman, J, Smirnov, O, Sobey, C, Steinmetz, M, Tagger, M, Tang, Y, Tasse, C, Vermeulen, R, Vocks, C, Wijers, RAMJ, Wise, MW, Wucknitz, O, and Zarka, P

Published
2013

6. Needle-like structures discovered on positively charged lightning branches.

Author

Hare BM, Scholten O, Dwyer J, Trinh TNG, Buitink S, Ter Veen S, Bonardi A, Corstanje A, Falcke H, Hörandel JR, Huege T, Mitra P, Mulrey K, Nelles A, Rachen JP, Rossetto L, Schellart P, Winchen T, Anderson J, Avruch IM, Bentum MJ, Blaauw R, Broderick JW, Brouw WN, Brüggen M, Butcher HR, Ciardi B, Fallows RA, de Geus E, Duscha S, Eislöffel J, Garrett MA, Grießmeier JM, Gunst AW, van Haarlem MP, Hessels JWT, Hoeft M, van der Horst AJ, Iacobelli M, Koopmans LVE, Krankowski A, Maat P, Norden MJ, Paas H, Pandey-Pommier M, Pandey VN, Pekal R, Pizzo R, Reich W, Rothkaehl H, Röttgering HJA, Rowlinson A, Schwarz DJ, Shulevski A, Sluman J, Smirnov O, Soida M, Tagger M, Toribio MC, van Ardenne A, Wijers RAMJ, van Weeren RJ, Wucknitz O, Zarka P, and Zucca P

Abstract

Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends-called positive and negative leaders 1 . Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30-300-megahertz frequency band 2-8 that can be remotely sensed and imaged with high spatial and temporal resolution 9-11 . Positive leaders propagate more continuously and thus emit very little high-frequency radiation 12 . Radio emission from positive leaders has nevertheless been mapped 13-15 , and exhibits a pattern that is different from that of negative leaders 11-13,16,17 . Furthermore, it has been inferred that positive leaders can become transiently disconnected from negative leaders 9,12,16,18-20 , which may lead to current pulses that both reconnect positive leaders to negative leaders 11,16,17,20-22 and cause multiple cloud-to-ground lightning events 1 . The disconnection process is thought to be due to negative differential resistance 18 , but this does not explain why the disconnections form primarily on positive leaders 22 , or why the current in cloud-to-ground lightning never goes to zero 23 . Indeed, it is still not understood how positive leaders emit radio-frequency radiation or why they behave differently from negative leaders. Here we report three-dimensional radio interferometric observations of lightning over the Netherlands with unprecedented spatiotemporal resolution. We find small plasma structures-which we call 'needles'-that are the dominant source of radio emission from the positive leaders. These structures appear to drain charge from the leader, and are probably the reason why positive leaders disconnect from negative ones, and why cloud-to-ground lightning connects to the ground multiple times.

Published
2019
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7. Corrigendum: A large light-mass component of cosmic rays at 10 17 -10 17.5 electronvolts from radio observations.

Author

Buitink S, Corstanje A, Falcke H, Hörandel JR, Huege T, Nelles A, Rachen JP, Rossetto L, Schellart P, Scholten O, Ter Veen S, Thoudam S, Trinh TN, Anderson J, Asgekar A, Avruch IM, Bell ME, Bentum MJ, Bernardi G, Best P, Bonafede A, Breitling F, Broderick JW, Brouw WN, Brüggen M, Butcher HR, Carbone D, Ciardi B, Conway JE, de Gasperin F, de Geus E, Deller A, Dettmar RJ, van Diepen G, Duscha S, Eislöffel J, Engels D, Enriquez JE, Fallows RA, Fender R, Ferrari C, Frieswijk W, Garrett MA, Grießmeier JM, Gunst AW, van Haarlem MP, Hassall TE, Heald G, Hessels JW, Hoeft M, Horneffer A, Iacobelli M, Intema H, Juette E, Karastergiou A, Kondratiev VI, Kramer M, Kuniyoshi M, Kuper G, van Leeuwen J, Loose GM, Maat P, Mann G, Markoff S, McFadden R, McKay-Bukowski D, McKean JP, Mevius M, Mulcahy DD, Munk H, Norden MJ, Orru E, Paas H, Pandey-Pommier M, Pandey VN, Pietka M, Pizzo R, Polatidis AG, Reich W, Röttgering HJ, Scaife AM, Schwarz DJ, Serylak M, Sluman J, Smirnov O, Stappers BW, Steinmetz M, Stewart A, Swinbank J, Tagger M, Tang Y, Tasse C, Toribio MC, Vermeulen R, Vocks C, Vogt C, van Weeren RJ, Wijers RA, Wijnholds SJ, Wise MW, Wucknitz O, Yatawatta S, Zarka P, and Zensus JA

Published
2016
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8. A large light-mass component of cosmic rays at 10(17)-10(17.5) electronvolts from radio observations.

Author

Buitink S, Corstanje A, Falcke H, Hörandel JR, Huege T, Nelles A, Rachen JP, Rossetto L, Schellart P, Scholten O, ter Veen S, Thoudam S, Trinh TN, Anderson J, Asgekar A, Avruch IM, Bell ME, Bentum MJ, Bernardi G, Best P, Bonafede A, Breitling F, Broderick JW, Brouw WN, Brüggen M, Butcher HR, Carbone D, Ciardi B, Conway JE, de Gasperin F, de Geus E, Deller A, Dettmar RJ, van Diepen G, Duscha S, Eislöffel J, Engels D, Enriquez JE, Fallows RA, Fender R, Ferrari C, Frieswijk W, Garrett MA, Grießmeier JM, Gunst AW, van Haarlem MP, Hassall TE, Heald G, Hessels JW, Hoeft M, Horneffer A, Iacobelli M, Intema H, Juette E, Karastergiou A, Kondratiev VI, Kramer M, Kuniyoshi M, Kuper G, van Leeuwen J, Loose GM, Maat P, Mann G, Markoff S, McFadden R, McKay-Bukowski D, McKean JP, Mevius M, Mulcahy DD, Munk H, Norden MJ, Orru E, Paas H, Pandey-Pommier M, Pandey VN, Pietka M, Pizzo R, Polatidis AG, Reich W, Röttgering HJ, Scaife AM, Schwarz DJ, Serylak M, Sluman J, Smirnov O, Stappers BW, Steinmetz M, Stewart A, Swinbank J, Tagger M, Tang Y, Tasse C, Toribio MC, Vermeulen R, Vocks C, Vogt C, van Weeren RJ, Wijers RA, Wijnholds SJ, Wise MW, Wucknitz O, Yatawatta S, Zarka P, and Zensus JA

Abstract

Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 10(17)-10(18) electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers--cascades of secondary particles in the atmosphere-and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 10(17)-10(17.5) electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 10(17.5) electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 10(17)-10(17.5) electronvolt range.

Published
2016
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9. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers.

Author

Schellart P, Trinh TN, Buitink S, Corstanje A, Enriquez JE, Falcke H, Hörandel JR, Nelles A, Rachen JP, Rossetto L, Scholten O, Ter Veen S, Thoudam S, Ebert U, Koehn C, Rutjes C, Alexov A, Anderson JM, Avruch IM, Bentum MJ, Bernardi G, Best P, Bonafede A, Breitling F, Broderick JW, Brüggen M, Butcher HR, Ciardi B, de Geus E, de Vos M, Duscha S, Eislöffel J, Fallows RA, Frieswijk W, Garrett MA, Grießmeier J, Gunst AW, Heald G, Hessels JW, Hoeft M, Holties HA, Juette E, Kondratiev VI, Kuniyoshi M, Kuper G, Mann G, McFadden R, McKay-Bukowski D, McKean JP, Mevius M, Moldon J, Norden MJ, Orru E, Paas H, Pandey-Pommier M, Pizzo R, Polatidis AG, Reich W, Röttgering H, Scaife AM, Schwarz DJ, Serylak M, Smirnov O, Steinmetz M, Swinbank J, Tagger M, Tasse C, Toribio MC, van Weeren RJ, Vermeulen R, Vocks C, Wise MW, Wucknitz O, and Zarka P

Abstract

We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields.

Published
2015
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10. Synchronous x-ray and radio mode switches: a rapid global transformation of the pulsar magnetosphere.

Author

Hermsen W, Hessels JW, Kuiper L, van Leeuwen J, Mitra D, de Plaa J, Rankin JM, Stappers BW, Wright GA, Basu R, Alexov A, Coenen T, Grießmeier JM, Hassall TE, Karastergiou A, Keane E, Kondratiev VI, Kramer M, Kuniyoshi M, Noutsos A, Serylak M, Pilia M, Sobey C, Weltevrede P, Zagkouris K, Asgekar A, Avruch IM, Batejat F, Bell ME, Bell MR, Bentum MJ, Bernardi G, Best P, Bîrzan L, Bonafede A, Breitling F, Broderick J, Brüggen M, Butcher HR, Ciardi B, Duscha S, Eislöffel J, Falcke H, Fender R, Ferrari C, Frieswijk W, Garrett MA, de Gasperin F, de Geus E, Gunst AW, Heald G, Hoeft M, Horneffer A, Iacobelli M, Kuper G, Maat P, Macario G, Markoff S, McKean JP, Mevius M, Miller-Jones JC, Morganti R, Munk H, Orrú E, Paas H, Pandey-Pommier M, Pandey VN, Pizzo R, Polatidis AG, Rawlings S, Reich W, Röttgering H, Scaife AM, Schoenmakers A, Shulevski A, Sluman J, Steinmetz M, Tagger M, Tang Y, Tasse C, ter Veen S, Vermeulen R, van de Brink RH, van Weeren RJ, Wijers RA, Wise MW, Wucknitz O, Yatawatta S, and Zarka P

Abstract

Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories.

Published
2013
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11. The vertical profile of winds on Titan.

Author

Bird MK, Allison M, Asmar SW, Atkinson DH, Avruch IM, Dutta-Roy R, Dzierma Y, Edenhofer P, Folkner WM, Gurvits LI, Johnston DV, Plettemeier D, Pogrebenko SV, Preston RA, and Tyler GL

Abstract

One of Titan's most intriguing attributes is its copious but featureless atmosphere. The Voyager 1 fly-by and occultation in 1980 provided the first radial survey of Titan's atmospheric pressure and temperature and evidence for the presence of strong zonal winds. It was realized that the motion of an atmospheric probe could be used to study the winds, which led to the inclusion of the Doppler Wind Experiment on the Huygens probe. Here we report a high resolution vertical profile of Titan's winds, with an estimated accuracy of better than 1 m s(-1). The zonal winds were prograde during most of the atmospheric descent, providing in situ confirmation of superrotation on Titan. A layer with surprisingly slow wind, where the velocity decreased to near zero, was detected at altitudes between 60 and 100 km. Generally weak winds (approximately 1 m s(-1)) were seen in the lowest 5 km of descent.

Published
2005
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