ORCID Profile
0000-0001-5909-0926
Current Organisation
University of Colorado at Boulder
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Publisher: American Geophysical Union (AGU)
Date: 24-08-2017
DOI: 10.1002/2017GL074587
Publisher: American Geophysical Union (AGU)
Date: 22-09-2018
DOI: 10.1029/2018GL079527
Abstract: A magnetic conjunction between Van Allen Probes spacecraft and the Balloon Array for Radiation‐belt Relativistic Electron Losses (BARREL) reveals the simultaneous occurrence of broadband Alfvénic fluctuations and multi‐timescale modulation of enhanced atmospheric X‐ray bremsstrahlung emission. The properties of the Alfvénic fluctuations are used to build a model for pitch angle scattering in the outer radiation belt on electron gyro‐radii scale field structures. It is shown that this scattering may lead to the transport of electrons into the loss cone over an energy range from hundreds of keV to multi‐MeV on diffusive timescales on the order of hours. This process may account for modulation of atmospheric X‐ray fluxes observed from balloons and constitute a significant loss process for the radiation belts.
Publisher: American Geophysical Union (AGU)
Date: 2021
DOI: 10.1029/2020JA028679
Abstract: We investigate the rare events of sudden appearances of relativistic electrons ( keV), which are normally confined to the Van Allen belts, in the slot region. The frequency of occurrence of these events is on average 1–2 per year. To cope with the scarcity of events, in this study, we examine 21 years of trapped relativistic electron fluxes available from the POES and MetOp Space Environment Monitor (SEM‐2). Our statistical analysis shows that these events can occur even during moderate geomagnetic activity. Occurrence of these events correlates with high‐speed solar winds or interplanetary coronal mass ejections depending on the phase of the solar cycle. A strong correlation of these events is found with ultra‐low frequency (ULF) wave activity, which can be used to predict these events with more than 75% accuracy.
Publisher: American Geophysical Union (AGU)
Date: 04-2017
DOI: 10.1002/2017JA024219
Publisher: American Astronomical Society
Date: 31-07-2023
Publisher: Authorea, Inc.
Date: 16-04-2023
DOI: 10.22541/ESSOAR.168167400.03912545/V1
Abstract: Pitch Angle Distributions in the radiation belts are well characterized with sinnα. By tracking the exponent ‘n’, termed Pitch Angle Index, we are able to observe persistent and cross energy changes in pitch angle distributions of Van Allen radiation belt electrons using Van Allen Probes particle observations. The pitch angle distributions measurements are well fit down to a single satellite spin, and therefore can track spatially and temporally confined changes to determine connection between particles and waves. We use the Van Allen Probes data in conjunction with Geostationary Operational Environmental Satellites (GOES) spacecraft and several ground magnetometer stations from Canadian Array for Realtime Investigations of Magnetic Activity (CARISMA) and Finnish pulsation magnetometer network of Sodankylä Geophysical Observatory (SGO) to connect particles that become very anisotropic to electromagnetic ion cyclotron (EMIC) waves during a quiet period over two days, June 26 and 27, 2013. The waves and peaks in the particle PADs are both long lasting but spatially separated, suggesting that wave particle interactions in the inner magnetosphere can occur for extend periods of time and have significant impact on the global radiation belts, even during otherwise geomagnetically quiet times and when wave activity is highly localized.
Publisher: American Geophysical Union (AGU)
Date: 11-2016
DOI: 10.1002/2016JA022918
Publisher: Wiley
Date: 16-09-2020
Publisher: American Geophysical Union (AGU)
Date: 10-2017
DOI: 10.1002/2017JA024487
Publisher: American Geophysical Union (AGU)
Date: 02-2019
DOI: 10.1029/2018JA026326
Abstract: We present the temporal evolution of electron Phase Space Density (PSD) in the outer radiation belt during the intense March 2015 geomagnetic storm. Comparing observed PSD profiles as a function of L* at fixed first, M, and second, K, adiabatic invariants with those produced by simulations is critical for determining the physical processes responsible for the outer radiation belt dynamics. Here we show that the bulk of the accelerated and enhanced outer radiation belt population consists of electrons with K 0.17 G 1/2 Re. For these electrons, the observed PSD versus L* profiles during the recovery phase of the storm have a positive radial gradient. We compare the observed temporal evolution of the PSD profiles during the recovery phase with those produced by radial diffusion simulations driven by observed Ultralow Frequency wave power as measured on the ground. Our results indicate that the dominant flux enhancement, inside L* 5, in the heart of the outer radiation belt during the March 2015 geomagnetic storm is consistent with that produced by fast inward radial diffusion of electrons from a dynamic outer boundary driven by enhanced Ultralow Frequency wave power.
No related grants have been discovered for DANIEL BAKER.