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Title: Origin and Properties of Quiet-time 0.11–1.28 MeV Nucleon{sup −1} Heavy-ion Population Near 1 au

Abstract

Using measurements from the Advanced Composition Explorer /Ultra-Low Energy Isotope Spectrometer near 1 au, we surveyed the composition and spectra of heavy ions (He-through-Fe) during quiet times from 1998 January 1 to 2015 December 31 at suprathermal energies between ∼0.11 and ∼1.28 MeV nucleon{sup −1}. The selected time period covers the maxima of solar cycles 23 and 24 and the extended solar minimum in between. We find the following. (1) The number of quiet hours in each year correlates well with the sunspot number, year 2009 was the quietest for about 82% of the time. (2) The composition of the quiet-time suprathermal heavy-ion population ({sup 3}He, C-through-Fe) correlates well with the level of solar activity, exhibiting SEP-like composition signatures during solar maximum, and CIR- or solar wind-like composition during solar minimum. (3) The heavy-ion (C–Fe) spectra exhibit suprathermal tails at energies of 0.11–0.32 MeV nucleon{sup −1} with power-law spectral indices ranging from 1.40 to 2.97. Fe spectra soften (steepen, i.e., spectral index increases) smoothly with increasing energies compared with Fe, indicating a rollover behavior of Fe at higher energies (0.45–1.28 MeV nucleon{sup −1}). (4) Spectral indices of Fe and O do not appear to exhibit clear solar cycle dependence. (2)more » and (3) imply that during IP quiet times and at energies above ∼0.1 MeV nucleon{sup −1}, the IP medium is dominated by material from prior solar and interplanetary events. We discuss the implications of these extended observations in the context of the current understanding of the suprathermal ion population near 1 au.« less

Authors:
; ;  [1];  [2];  [3]
  1. Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX 78238 (United States)
  2. Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723 (United States)
  3. Department of Physics, College of Applied and Supporting Studies, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)
Publication Date:
OSTI Identifier:
22663946
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ACCELERATION; COMPARATIVE EVALUATIONS; HEAVY IONS; HELIUM 3; MEV RANGE; NUCLEONS; PARTICLES; SOLAR CYCLE; SOLAR WIND; SPECTRA; SPECTROMETERS; SUN; SUNSPOTS

Citation Formats

Dayeh, M. A., Desai, M. I., Ebert, R. W., Mason, G. M., and Farahat, A., E-mail: maldayeh@swri.edu. Origin and Properties of Quiet-time 0.11–1.28 MeV Nucleon{sup −1} Heavy-ion Population Near 1 au. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/155.
Dayeh, M. A., Desai, M. I., Ebert, R. W., Mason, G. M., & Farahat, A., E-mail: maldayeh@swri.edu. Origin and Properties of Quiet-time 0.11–1.28 MeV Nucleon{sup −1} Heavy-ion Population Near 1 au. United States. doi:10.3847/1538-4357/835/2/155.
Dayeh, M. A., Desai, M. I., Ebert, R. W., Mason, G. M., and Farahat, A., E-mail: maldayeh@swri.edu. Wed . "Origin and Properties of Quiet-time 0.11–1.28 MeV Nucleon{sup −1} Heavy-ion Population Near 1 au". United States. doi:10.3847/1538-4357/835/2/155.
@article{osti_22663946,
title = {Origin and Properties of Quiet-time 0.11–1.28 MeV Nucleon{sup −1} Heavy-ion Population Near 1 au},
author = {Dayeh, M. A. and Desai, M. I. and Ebert, R. W. and Mason, G. M. and Farahat, A., E-mail: maldayeh@swri.edu},
abstractNote = {Using measurements from the Advanced Composition Explorer /Ultra-Low Energy Isotope Spectrometer near 1 au, we surveyed the composition and spectra of heavy ions (He-through-Fe) during quiet times from 1998 January 1 to 2015 December 31 at suprathermal energies between ∼0.11 and ∼1.28 MeV nucleon{sup −1}. The selected time period covers the maxima of solar cycles 23 and 24 and the extended solar minimum in between. We find the following. (1) The number of quiet hours in each year correlates well with the sunspot number, year 2009 was the quietest for about 82% of the time. (2) The composition of the quiet-time suprathermal heavy-ion population ({sup 3}He, C-through-Fe) correlates well with the level of solar activity, exhibiting SEP-like composition signatures during solar maximum, and CIR- or solar wind-like composition during solar minimum. (3) The heavy-ion (C–Fe) spectra exhibit suprathermal tails at energies of 0.11–0.32 MeV nucleon{sup −1} with power-law spectral indices ranging from 1.40 to 2.97. Fe spectra soften (steepen, i.e., spectral index increases) smoothly with increasing energies compared with Fe, indicating a rollover behavior of Fe at higher energies (0.45–1.28 MeV nucleon{sup −1}). (4) Spectral indices of Fe and O do not appear to exhibit clear solar cycle dependence. (2) and (3) imply that during IP quiet times and at energies above ∼0.1 MeV nucleon{sup −1}, the IP medium is dominated by material from prior solar and interplanetary events. We discuss the implications of these extended observations in the context of the current understanding of the suprathermal ion population near 1 au.},
doi = {10.3847/1538-4357/835/2/155},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}
  • Using measurements from the Advanced Composition Explorer/Ultra-Low Energy Isotope Spectrometer (ACE/ULEIS) near 1 AU, we surveyed the composition and spectra of heavy ions (He-through-Fe) during interplanetary quiet times from 1998 January 1 to 2014 December 31 at suprathermal energies between ∼0.11 and ∼1.28 MeV nucleon{sup −1}. The selected time period covers the maxima of solar cycles 23 and 24 and the extended solar minimum in between. We find the following: (1) The number of quiet-hours in each year correlates well with the sunspot number, year 2009 was the quietest for about 90% of the time; (2) The composition of the quiet-timemore » suprathermal heavy ion population ({sup 3}He, C-through-O, and Fe) correlates well with the level of solar activity, exhibiting SEP-like composition signatures during solar maximum, and CIR- or solar wind-like composition during solar minimum; (3) The heavy ion spectra at ∼0.11-0.32 MeV nucleon{sup −1} exhibit suprathermal tails with power-law spectral indices ranging from 1.4 to 2.7. (4) Fe spectral indices get softer (steeper) from solar minimum of cycle 23 to solar cycle 24 maximum. These results imply that during IP quiet times and at energies above ∼0.1 MeV nucleon{sup −1}, the IP medium is dominated by material from prior solar and interplanetary events.« less
  • The relative abundances of the nuclei B-Si, the group P-V, and the group Cr-Ni (the iron group) have been measured with an instrument on the OGO-5 satellite in the energy range approx.10 to 60 MeV nucleonmore » $sup -1$ in the period of changing solar modulation in the 1968--1971. Stringent criteria were applied for the selection of interplanetary quiet-time data in order to eliminate the highly variable solar component. The purpose of the investigation was to obtain evidence for the solar or galactic origin of the nuclei in this energy range where it is known that the H and He spectra display striking differences in shape from the galactic cosmic-ray spectra at higher energies. We find that: (1) The relative abundances are in good agreement with nuclear abundances of the galactic cosmic rays. For example, since we find that boron has an abundance relative to oxygen which is characteristic of the secondary nuclei in the galactic radiation, the component we are measuring is not characteristic of solar abundances. (2) The differential energy spectra of C and O are found to diverge at these low energies from the characteristic modulated galactic spectra; i.e., if J proportional E/sup gamma/ represents the spectra form in this energy region, with $gamma$=1.0 at the higher energies, we find $gamma$$Yields$0 with decreasing energy. (3) During the change in solar cycle modulation from 1968 to 1971, the changes in C+N+O flux were observed to undergo a phase lag in time with respect to the high-energy galactic cosmic rays which was the same as the phase lag for helium nuclei of galactic origin in the energy range 30 to 100 MeV nucleon$sup - 1$. These measurements were extended to a brief period in 1972. (AIP)« less
  • The abundances and spectra of 1-10 MeV per nucleon protons, He-3, He-4, C, O, and Fe have been examined during solar quiet periods from 1978 to 1987 in an effort to investigate the recent suggestion by Wenzel et al. (1990) that the ions may be of solar origin. It is found that the intensities of the ions, other than O, fall by an order of magnitude between solar maximum and solar minimum, and that the greater than 1 MeV per nucleon ions exhibit weak streaming away from the sun. More significantly, the quiet-time ions during solar maximum have He-3-rich andmore » Fe-rich abundances which are established characteristics of small impulsive solar flares. Thus, it is suggested that small unresolved impulsive flares make a substantial contribution to the quiet-time fluxes. He-4 from these flares may also contribute strongly to the ion spectra that were reported for the 35-1600 keV energy range by Wenzel et al. 18 refs.« less
  • We examine the longitude distribution of and relationship between interplanetary (IP) shock properties and ∼0.1–20 MeV nucleon{sup -1} O and Fe ions during seven multi-spacecraft energetic storm particle (ESP) events at 1 au. These ESP events were observed at two spacecraft and were primarily associated with low Mach number, quasi-perpendicular shocks. Key observations include the following: (i) the Alfvén Mach number increased from east to west of the coronal mass ejection source longitude, while the shock speed, compression ratios, and obliquity showed no clear dependence; (ii) the O and Fe time intensity profiles and peak intensities varied significantly between longitudinallymore » separated spacecraft observing the same event, the peak intensities being larger near the nose and smaller along the flank of the IP shock; (iii) the O and Fe peak intensities had weak to no correlations with the shock parameters; (iv) the Fe/O time profiles showed intra-event variations upstream of the shock that disappeared downstream of the shock, where values plateaued to those comparable to the mean Fe/O of solar cycle 23; (v) the O and Fe spectral index ranged from ∼1.0 to 3.4, the Fe spectra being softer in most events; and (vi) the observed spectral index was softer than the value predicted from the shock compression ratio in most events. We conclude that while the variations in IP shock properties may account for some variations in O and Fe properties within these multi-spacecraft events, detailed examination of the upstream seed population and IP turbulence, along with modeling, are required to fully characterize these observations.« less