Electron Transport During Solar Flares

Lee, Jeongwoo

doi:10.1007/1-4020-2814-8_9

Cited by 4 publications

(2 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The EIT images at a larger field-of-view (FOV) show a coronal hole north of the AR and nearby active regions at its south, and this event was accompanied by a narrow coronal mass ejection. The EUV images here reveal a large magnetic loop connecting the two spots, in which case the energetic electrons can access a wide range of magnetic field regions (Lee 2004). This result is consistent with a high degree of magnetic field inhomogeneity, α ≈ 0.6, as found in the present spectral analysis of the OVSA data.…”

Section: Eit Imagesmentioning

confidence: 73%

Analysis of Solar Microwave Burst Spectrum, I. Nonuniform Magnetic Field

Lee

2018

Journal of Astronomy and Space Sciences

Self Cite

View full text Add to dashboard Cite

Solar microwave bursts carry information about the magnetic field in the emitting region as well as about electrons accelerated during solar flares. While this sensitivity to the coronal magnetic field must be a unique advantage of solar microwave burst observations, it also adds a complexity to spectral analysis targeted to electron diagnostics. This paper introduces a new spectral analysis procedure in which the cross-section and thickness of a microwave source are expressed as power-law functions of the magnetic field so that the degree of magnetic inhomogeneity can systematically be derived. We applied this spectral analysis tool to two contrasting events observed by the Owens Valley Solar Array: the SOL2003-04-04T20:55 flare with a steep microwave spectrum and the SOL2003-10-19T16:50 flare with a broader spectrum. Our analysis shows that the strong flare with the broader microwave spectrum occurred in a region of highly inhomogeneous magnetic field and vice versa. We further demonstrate that such source properties are consistent with the magnetic field observations from the Michelson Doppler Imager instrument onboard the Solar and Heliospheric Observatory (SOHO) spacecraft and the extreme ultraviolet imaging observations from the SOHO extreme ultraviolet imaging telescope. This spectral inversion tool is particularly useful for analyzing microwave flux spectra of strong flares from magnetically complex systems.

show abstract

Section: Eit Imagesmentioning

confidence: 73%

Analysis of Solar Microwave Burst Spectrum, I. Nonuniform Magnetic Field

Lee

2018

Journal of Astronomy and Space Sciences

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, the time delay (100 s) that we found for the second precursor is unusually long. In a more general approach, Lee (2005) suggested that the trapping effect can be severe for strongly converging magnetic fields and extended electron ejection times, in which case our observation may possibly be explained. We anticipate that the present observation would motivate theoretical modeling of magnetic evolution combined with the participation of the thermal process in the future.…”

Section: Compared To Goes Sxr and Aia Euv Rhessi Hxrmentioning

confidence: 81%

Multi-instrument Comparative Study of Temperature, Number Density, and Emission Measure during the Precursor Phase of a Solar Flare

Liu

Jing

et al. 2022

ApJ

View full text Add to dashboard Cite

We present a multi-instrument study of the two precursor brightenings prior to the M6.5 flare (SOL2015-06-22T18:23) in the NOAA Active Region 12371, with a focus on the temperature (T), electron number density (n), and emission measure (EM). The data used in this study were obtained from four instruments with a variety of wavelengths, i.e., the Solar Dynamics Observatory’s Atmospheric Imaging Assembly (AIA), in six extreme ultraviolet (EUV) passbands; the Expanded Owens Valley Solar Array (EOVSA) in microwave (MW); the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in hard X-rays (HXR); and the Geostationary Operational Environmental Satellite (GOES) in soft X-rays (SXR). We compare the temporal variations of T, n, and EM derived from the different data sets. Here are the key results. (1) GOES SXR and AIA EUV have almost identical EM variations (1.5–3 × 1048 cm−3) and very similar T variations, from 8 to 15 million Kelvin (MK). (2) Listed from highest to lowest, EOVSA MW provides the highest temperature variations (15–60 MK), followed by RHESSI HXR (10–24 MK), then GOES SXR and AIA EUV (8–15 MK). (3) The EM variation from the RHESSI HXR measurements is always less than the values from AIA EUV and GOES SXR by at most 20 times. The number density variation from EOVSA MW is greater than the value from AIA EUV by at most 100 times. The results quantitatively describe the differences in the thermal parameters at the precursor phase, as measured by different instruments operating at different wavelength regimes and for different emission mechanisms.

show abstract

Spatial Evidence for Transition Radiation in a Solar Radio Burst

Nita

Gary

Fleishman

2005

ApJ

View full text Add to dashboard Cite

Microturbulence, i.e. enhanced fluctuations of plasma density, electric and magnetic fields, is of great interest in astrophysical plasmas, but occurs on spatial scales far too small to resolve by remote sensing, e.g., at ~ 1-100 cm in the solar corona. This paper reports spatially resolved observations that offer strong support for the presence in solar flares of a suspected radio emission mechanism, resonant transition radiation, which is tightly coupled to the level of microturbulence and provides direct diagnostics of the existence and level of fluctuations on decimeter spatial scales. Although the level of the microturbulence derived from the radio data is not particularly high, <\Delta n^2 >/n^2 ~ 10^{-5}$, it is large enough to affect the charged particle diffusion and give rise to effective stochastic acceleration. This finding has exceptionally broad astrophysical implications since modern sophisticated numerical models predict generation of much stronger turbulence in relativistic objects, e.g., in gamma-ray burst sources.Comment: 13 pages, 4 figures, ApJL accepte

show abstract

Electron Transport During Solar Flares

Cited by 4 publications

References 61 publications

Analysis of Solar Microwave Burst Spectrum, I. Nonuniform Magnetic Field

Analysis of Solar Microwave Burst Spectrum, I. Nonuniform Magnetic Field

Multi-instrument Comparative Study of Temperature, Number Density, and Emission Measure during the Precursor Phase of a Solar Flare

Spatial Evidence for Transition Radiation in a Solar Radio Burst

Contact Info

Product

Resources

About