Current Sheet Regulation of Solar Near-Relativistic Electron Injection Histories |
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Neus Agueda Submitted: 2013-01-28 04:57
We present a sample of three large near-relativistic (>50 keV) electron events observed in 2001 by both the ACE and the Ulysses spacecraft, when Ulysses was at high-northern latitudes (>60?) and close to 2 AU. Despite the large latitudinal distance between the two spacecraft, electrons injected near the Sun reached both heliospheric locations. All three events were associated with large solar flares, strong decametric type II radio burst and accompanied by wide (>212?) and fast (>1400 km s-1) coronal mass ejections (CMEs).
We use advanced interplanetary transport simulations and make use of the directional intensities observed in-situ by the spacecraft, to infer the electron injection profile close to the Sun and the interplanetary transport conditions at both low and high latitudes. For the three selected events, we find similar interplanetary transport conditions at different heliolatitudes for a given event, with values of the mean free path ranging from 0.04 AU to 0.27 AU.
We find differences in the injection profiles inferred for each spacecraft. We investigate the role that sector boundaries of the heliospheric current sheet (HCS) have on determining the characteristics of the electron injection profiles. Extended injection profiles, associated with coronal shocks, are found if the magnetic footpoints of the spacecraft lay in the same magnetic sector as the associated flare, while intermittent sparse injection episodes appear when the spacecraft footpoints are in the opposite sector or a wrap in the HCS bounded the CME structure.
Authors: N. Agueda, R. Vainio, S. Dalla, D. Lario, B. Sanahuja
Projects: ACE
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Publication Status: Accepted
Last Modified: 2013-01-28 09:28
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A Database of >20 keV Electron Green's Functions of Interplanetary Transport at 1 AU |
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Neus Agueda Submitted: 2012-10-01 07:56
We use interplanetary transport simulations to compute a database of electron Green's functions, i.e., differential intensities resulting at the spacecraft position from an impulsive injection of energetic (>20 keV) electrons close to the Sun, for a large number of values of two standard interplanetary transport parameters: the scattering mean free path and the solar wind speed. The nominal energy channels of the ACE, STEREO, and Wind spacecraft have been used in the interplanetary transport simulations to conceive a unique tool for the study of near-relativistic electron events observed at 1 AU. In this paper, we quantify the characteristic times of the Green's functions (onset and peak time, rise and decay phase duration) as a function of the interplanetary transport conditions. We use the database to calculate the FWHM of the pitch-angle distributions at different times of the event and under different scattering conditions. This allows us to provide a first quantitative result that can be compared with observations, and to assess the validity of the frequently used term beam-like pitch-angle distribution.
Authors: Agueda N., Vainio R., Sanahuja B.
Projects: ACE,STEREO,Wind
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Publication Status: ApJS, 202, 18, 2012
Last Modified: 2012-10-01 10:52
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Subject will be restored when possible |
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Neus Agueda Submitted: 2007-12-10 02:04
We present a Monte Carlo method to model the transport of solar nearrelativistic electrons in the interplanetary medium, including adiabatic focusing, pitch-angle dependent scattering, and solar wind effects. By taking into account the angular response of the LEFS60 telescope of the EPAM instrument on board the ACE spacecraft, we transform the simulated pitch-angle distributions into the sectored intensities measured by the telescope. The goal is to deconvolve the effects of the interplanetary transport in order to infer the underlying injection profile and the radial mean free path of the electrons.
We apply the model to the near-relativistic electron event observed on 2000 May 1, associated with an impulsive X-ray flare, type III radio bursts, and a narrow fast CME. The deconvolved interplanetary transport conditions reveal a long radial mean free path of 0.9 AU and pitch-angle dependent scattering. The eight observed sectored intensities are fitted in detail for more than 90 min, except for a short period (∼12 min) right after the time of peak intensities. This discrepancy may suggest that the assumed scattering model performs more efficiently than the actual scattering processes at work. The resulting injection profile consists of two main components, an initial component lasting 2-3 min and probably related to a type III radio burst observed by WIND/WAVES at ∼10:21 UT, and a delayed component starting at the Sun around 10:35 UT with a typical injection decay time scale of ∼0.5 h. The delayed component may be related to the CME-driven shock.
Authors: N. Agueda, R. Vainio, D. Lario, and B. Sanahuja
Projects: None
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Publication Status: ApJ (in press)
Last Modified: 2007-12-10 11:17
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