13 results on '"Tesema, F."'
Search Results
2. Dayside Pc2 Waves Associated With Flux Transfer Events in a 3D Hybrid‐Vlasov Simulation.
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Tesema, F., Palmroth, M., Turc, L., Zhou, H., Cozzani, G., Alho, M., Pfau‐Kempf, Y., Horaites, K., Zaitsev, I., Grandin, M., Battarbee, M., Ganse, U., Workayehu, A., Suni, J., Papadakis, K., Dubart, M., and Tarvus, V.
- Subjects
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MAGNETIC reconnection , *GEOMAGNETISM , *MAGNETOPAUSE , *OCEAN wave power , *MAGNETOSPHERE , *SOLAR wind - Abstract
Flux transfer events (FTEs) are transient magnetic flux ropes at Earth's dayside magnetopause formed due to magnetic reconnection. As they move across the magnetopause surface, they can generate disturbances in the ultralow frequency (ULF) range, which then propagate into the magnetosphere. This study provides evidence of ULF waves in the Pc2 wave frequency range (>0.1 Hz) caused by FTEs during dayside reconnection using a global 3D hybrid‐Vlasov simulation (Vlasiator). These waves resulted from FTE formation and propagation at the magnetopause are particularly associated with large, rapidly moving FTEs. The wave power is stronger in the morning than afternoon, showing local time asymmetry. In the pre and postnoon equatorial regions, significant poloidal and toroidal components are present alongside the compressional component. The noon sector, with fewer FTEs, has lower wave power and limited magnetospheric propagation. Plain Language Summary: The Earth's magnetosphere is a dynamic region shaped by the interplay between the solar wind and Earth's magnetic field. This interaction occurs at the boundary of the magnetosphere (magnetopause) through a process known as magnetic reconnection, giving rise to Flux Transfer Events (FTEs), which are magnetic structures that carry flux and energy into the magnetosphere. These FTEs form either in sudden bursts, patchy patterns or in a continuous, and relatively stable way making the magnetopause surface dynamic. As the FTEs move along the boundary of the magnetosphere, they create compressed regions and lead to wave generation that can extend into the magnetosphere. The study uses an advanced 3D hybrid‐Vlasov simulation model to analyze waves originated from FTE formation and propagation at the magnetopause. We find that rapidly moving and large FTEs have a significant impact on the magnetopause, leading to the generation of ULF waves with frequency above 0.1 Hz. This shows first direct evidence supporting previous theoretical speculations regarding the ability of FTEs to generate waves near the magnetopause. Key Points: Dayside Pc2 waves (>0.1 Hz) have been detected in a 3D hybrid‐Vlasov simulationThese waves exhibit lower intensity within the magnetosphere at noon, compared to the prenoon and postnoon sectorsPc2 waves observed in the simulation are associated with largest and fast moving flux transfer events initiated by subsolar reconnection [ABSTRACT FROM AUTHOR]
- Published
- 2024
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3. The response of the ionosphere to intense geomagnetic storms in 2012 using GPS-TEC data from East Africa longitudinal sector
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Tesema, F., Damtie, B., and Nigussie, M.
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- 2015
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4. Six-dimensional view of Earth’s magnetosphere with the Vlasiator simulation
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Turc, L., Palmroth, M., Grandin, M., Horaites, K., Alho, M., Battarbee, M., Bussov, M., Cozzani, G., Dubart, M., Ganse, U., Gordeev, E., Papadakis, K., Pfau-Kempf, Y., Suni, J., Tarvus, V., Tesema, F., Zaitsev, I., and Zhou, H.
- Abstract
Vlasiator is a hybrid-Vlasov model designed for global simulations of Earth's magnetosphere. In the hybrid-Vlasov approach, ions are described as velocity distribution functions and electrons are a charge-neutralising fluid. This provides a self-consistent description of ion dynamics in the global magnetospheric context. Vlasiator simulations have been at first confined to two dimensions in ordinary space (2D) and three in velocity space (3V), due to their high computational cost. The recent implementation of adaptive mesh refinement now makes it possible to run 6D (3D-3V) global simulations of Earth's magnetosphere. Here we present an overview of recent results obtained with these new 6D simulations, pertaining to magnetotail dynamics, magnetopause motion, and particle precipitation into the ionosphere. The runs are carried out with a purely southward interplanetary magnetic field, which is conducive to dayside and nightside reconnection. On the dayside, we find that cusp proton precipitation is modulated by flux transfer events formed by magnetopause reconnection. In the magnetotail, the global simulation reveals the interplay between instabilities and reconnection, and their combined role in global magnetotail reconfiguration. We also study the motion of the magnetopause in response to an enhancement in the solar wind dynamic pressure., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)
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- 2023
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5. Spatial filtering in a 6D hybrid-Vlasov scheme for alleviating AMR artifacts (in discussion)
- Author
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Papadakis, K., Pfau-Kempf, Y., Ganse, U., Battarbee, M., Alho, M., Grandin, M., Dubart, M., Turc, L., Zhou, H., Horaites, K., Zaitsev, I., Cozzani, G., Bussov, M., Gordeev, E., Tesema, F., George, H., Suni, J, Tarvus, V., and Palmroth, M.
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- 2022
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6. Context Matters for Food Security: Multi-Sited Evidence of Shared Cultural Models of Food Consumption
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Owens, C., primary, Weaver, L.J., additional, Kaiser, B.N., additional, Kalk, T., additional, Tesema, F., additional, Tessema, F., additional, and Hadley, C., additional
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- 2021
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7. Observations of precipitation energies during different types of pulsating aurora
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Tesema, F. (Fasil), Partamies, N. (Noora), Tyssøy, H. N. (Hilde Nesse), McKay, D. (Derek), Tesema, F. (Fasil), Partamies, N. (Noora), Tyssøy, H. N. (Hilde Nesse), and McKay, D. (Derek)
- Abstract
Pulsating aurora (PsA) is a diffuse type of aurora with different structures switching on and off with a period of a few seconds. It is often associated with energetic electron precipitation (>10 keV) resulting in the interaction between magnetospheric electrons and electromagnetic waves in the magnetosphere. Recent studies categorize pulsating aurora into three different types — amorphous pulsating aurora (APA), patchy pulsating aurora (PPA), and patchy aurora (PA) — based on the spatial extent of pulsations and structural stability. Differences in precipitation energies of electrons associated with these types of pulsating aurora have been suggested. In this study, we further examine these three types of pulsating aurora using electron density measurements from the European Incoherent Scatter (EISCAT) VHF/UHF radar experiments and Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) cosmic noise absorption (CNA) measurements. Based on ground-based all-sky camera images over the Fennoscandian region, we identified a total of 92 PsA events in the years between 2010 and 2020 with simultaneous EISCAT experiments. Among these events, 39, 35, and 18 were APA, PPA, and PA types with a collective duration of 58, 43, and 21 h, respectively. We found that, below 100 km, electron density enhancements during PPAs and PAs are significantly higher than during APA. However, there are no appreciable electron density differences between PPA and APA above 100 km, while PA showed weaker ionization. The altitude of the maximum electron density also showed considerable differences among the three types, centered around 110, 105, and 105 km for APA, PPA, and PA, respectively. The KAIRA CNA values also showed higher values on average during PPA (0.33 dB) compared to PA (0.23 dB) and especially APA (0.17 dB). In general, this suggests that the precipitating electrons responsible for APA have a lower energy range compared to PPA and PA types. Among the three categories, the mag
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- 2020
8. Observations of electron precipitation during pulsating aurora and its chemical impact
- Author
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Tesema, F. (Fasil), Partamies, N. (Noora), Tyssøy, H. N. (H. Nesse), Kero, A. (Antti), Smith-Johnsen, C. (C.), Tesema, F. (Fasil), Partamies, N. (Noora), Tyssøy, H. N. (H. Nesse), Kero, A. (Antti), and Smith-Johnsen, C. (C.)
- Abstract
Pulsating auroras (PsAs) are low‐intensity diffuse aurora, which switch on and off with a quasiperiodic oscillation period from a few seconds to ∼10 s. They are predominantly observed after magnetic midnight, during the recovery phase of substorms and at the equatorward boundary of the auroral oval. PsAs are caused by precipitating energetic electrons, which span a wide range of energies between tens and hundreds of keV. Such energetic PsA electrons will deposit their energy at mesospheric altitudes and induce atmospheric chemical changes. To examine the effects of energetic PsA electrons on the atmosphere, we first collect electron flux and energy measurements from low‐latitude spacecraft to construct a typical energy spectrum of precipitating electrons during PsA. Among the 840 PsA events identified using ground‐based auroral all‐sky camera (ASC) network over the Fennoscandian region, 253 events were observed by DMSP, POES, and FAST spacecraft over the common field of view of five ASCs. The combined measurements from these spacecraft enable us to obtain an energy spectrum consisting of nonrelativistic and relativistic (30 eV to 1,000 keV) electrons during PsA. The median spectrum was found to be in good agreement with earlier estimates of the PsA spectra. We then use the Sodankylä Ion‐neutral Chemistry (SIC) model to assess the chemical effect of PsA electrons. The observed extreme and median spectra of PsA produce a significant depletion in the mesospheric odd oxygen concentration up to 78%.
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- 2020
9. Context Matters for Food Security: Multi-Sited Evidence of Shared Cultural Models of Food Consumption.
- Author
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Owens, C., Weaver, L.J., Kaiser, B.N., Kalk, T., Tesema, F., Tessema, F., and Hadley, C.
- Subjects
FOOD security ,SOCIAL impact ,CONSUMPTION (Economics) ,FOOD consumption ,URBAN research ,SOCIAL context - Abstract
Anthropologists have long emphasized the social significance of foods and the contexts in which they are consumed. Expanding on this idea, we define the context of consumption as the non-eating behaviors that surround eating, such as the manner of food preparation, food sharing, and dietary patterns. In this study, we used cultural consensus analysis to assess whether there exist consistently shared, normative ideas about preferable context of food consumption in three diverse research sites: urban Ethiopia, rural Brazil, and rural Haiti. Our analysis demonstrates that in all three communities, there are distinct sets of behaviors that people identified as non-preferable because they reliably associate them with poverty and food insecurity, and behaviors that people identify as preferable because they reliably associate them with wealth and food security. Across the settings, there was little variation in agreement about behaviors across household composition, age, gender, and food security status. These findings suggest that people do indeed share culturally specific ideas about the context in which foods should be prepared and consumed, beyond the actual content of one's diet. Exploring these cultural models elucidates the social consequences of food insecurity, enabling researchers to better examine the relationship between food insecurity, social context, and well-being. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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10. Corrigendum to “Thermospheric winds over Abuja during solar minimum period” [Adv. Space Res. 65(5) (2020) 1424–1431]
- Author
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Sivla, W.T., primary, Ogunjobi, O., additional, and Tesema, F., additional
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- 2020
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11. 5G Mixed Mode: NR Multicast-Broadcast Services
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Garro, E., primary, Fuentes, M., additional, Carcel, J. L., additional, Chen, H., additional, Mi, D., additional, Tesema, F., additional, Gimenez, J. J., additional, and Gomez-Barquero, D., additional
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- 2020
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12. (109) AS SEEN ON TIKTOK: PERCEPTIONS AND UNDERSTANDINGS OF HORMONAL CONTRACEPTIVES ON SOCIAL MEDIA.
- Author
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Kalifa, N, Beil, J, Tesema, F, and Watkins, S E
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FAMILY planning services , *SOCIAL media , *PHYSICIANS' assistants , *CHILDBEARING age , *CONTRACEPTIVES , *MIDWIVES , *MEDICAL personnel - Abstract
Introduction: Contraception plays an integral role in many women's lives and is essential for family planning and treatment of myriad health conditions. Between 2017-2019, approximately 65% of women aged 15 to 49 in the United States were actively using a form of birth control. Social media has a significant influence over the contraceptive choices of many reproductive-aged women. TikTok, a platform established in 2017, is one of the fastest growing worldwide social media applications. In 2018, it was recognized in top charts as "Most Downloaded", and by 2023, approximately 150 million Americans became active users. Beyond its entertainment value, TikTok serves as a communication platform to nearly 5 million businesses, and the healthcare sector is no exception. Objective: This study assessed the attitudes and information users share about hormonal contraceptives (HC) on TikTok, to elucidate the type of information women are receiving. Additionally, the potential for healthcare providers to use this platform as a means to educate and reach millions of patients was explored. Methods: Apify, a free data-scraping tool, was used to automatically extract and compile 593 TikTok videos. Frequently searched hashtags, such as #birthcontrol, #hormonalcontraceptive, and #pregnancyprevention, were utilized to identify videos. Inclusion criteria included videos from US-based content creators and videos with English audio or text. The number of views and shares, length of video, and location of content creator for each TikTok were populated by the online application and imported onto RedCap for data collection. Demographic data such as gender and what type of content creator was providing the information, along with topics being portrayed and characteristics of each video, were also collected on RedCap. Results: 150 TikTok videos met our inclusion criteria. The average length of each TikTok was 47.08 seconds. The average number of views and shares were 4,623,942 and 9,952, respectively. The predominant HCs discussed were intrauterine devices (IUDs), depo-provera injections, and contraceptive implants. Prevalent themes included negative personal anecdotes, general health information, and side effects. Additionally, the most common characteristics of the Tiktoks were humor and education. Most of the content creators were female (91%), and non-medical professionals (62%). Of the videos created by medical professionals, 25% were created by physicians, 26% by nurse practitioners, followed by nurse midwives (19%), physician assistants (14%), and registered nurses (5%). Conclusions: Through short and engaging videos, TikTok has the ability to reach a wide and diverse audience. Oftentimes, users create TikToks that reveal their concerns, frustrating encounters, and how side effects impact their lives. Further studies may include determining how personal experiences of HC influence TikTok users' acceptability, adherence, and attitudes. Given its reach, medical professionals should consider using the platform to engage with patients and provide evidence based education regarding HC. Disclosure: No. [ABSTRACT FROM AUTHOR]
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- 2024
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13. Do People Agree on What Foods are Prestigious? Evidence of a Single, Shared Cultural Model of Food in Urban Ethiopia and Rural Brazil.
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Hadley C, Weaver LJ, Tesema F, and Tessema F
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- Adolescent, Adult, Aged, Aged, 80 and over, Brazil, Consensus, Demography, Ethiopia, Family Characteristics, Female, Food Supply, Humans, Male, Mental Health, Middle Aged, Surveys and Questionnaires, Young Adult, Attitude, Culture, Diet, Feeding Behavior, Rural Population, Social Class, Urban Population
- Abstract
To what extent do people agree on the meaning of foods, and does this vary by socioeconomic status, demographics, or household type? Addressing this question is critical for testing hypotheses about the relationship between food insecurity, food meaning, and mental well-being because it speaks directly to the social implications of food behaviors. In this study, we test for a shared cultural model of food meaning in two diverse settings: urban Ethiopia and rural Brazil. Using freelist and pile sort data from 63 respondents in Ethiopia and 62 from Brazil, we show strong consensus on the prestige value of various key food items in each context. Further, consensus varies little across household composition, food security status, and age and gender. This suggests that, in these two settings, consumption of widely available foods is an act that has both biological and social consequences.
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- 2019
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