Magnetic energy conversion, magnetospheric substorms and solar flares

Nature ◽  
1980 ◽  
Vol 284 (5753) ◽  
pp. 248-249 ◽  
Author(s):  
S.-I. Akasofu
Keyword(s):  
Energy Conversion ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Magnetospheric Substorms

scholarly journals Magnetic-field annihilation and island formation in electron-scale current sheet in Earth's magnetotail

2020 ◽  
Author(s):  
Hiroshi Hasegawa ◽  
Richard Denton ◽  
Kevin Genestreti ◽  
Takuma Nakamura ◽  
Tai Phan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Conversion ◽  
Current Sheet ◽  
Magnetic Energy ◽  
Particle Energy ◽  
Planar Geometry ◽  
Diffusion Region ◽  
Magnetospheric Substorms ◽  
Flow Energy ◽  
The Impact

Abstract Establishing the mechanism of magnetic-to-particle energy conversion through magnetic reconnection in current sheets1 is the key to understanding the impact of fast release of magnetic energy in many space and astrophysical plasma systems, such as during magnetospheric substorms2,3. It is generally believed that an electron-scale diffusion region (EDR), where a magnetic-to-electron energy conversion occurs, has an X-type magnetic-field geometry4 around which the energy of anti-parallel magnetic fields injected is mostly converted to the bulk-flow energy of electrons by magnetic tension of reconnected field-lines5,6. However, it is at present unknown exactly how this energy conversion occurs in EDRs, because there has been no observational method to fully address this problem. Here we present state-of-the-art analysis of multi-spacecraft observations in Earth’s magnetotail of an electron-scale current sheet, which demonstrates that contrary to the standard model of reconnection with an X-type EDR geometry, the fast energy conversion in the detected EDR was caused mostly by magnetic-field annihilation, rather than reconnection. Furthermore, we detected a magnetic island forming in the EDR itself, implying that the EDR had an elongated shape ideal for island generation7 and magnetic-field annihilation. The experimental discovery of the annihilation-dominated EDR reveals a new form of energy conversion in the reconnection process that can occur when the EDR has evolved from the X-type to planar geometry.

Observed signatures of magnetic energy conversion in solar flares and microflares

1990 ◽  
Vol 10 (9) ◽  
pp. 115-120 ◽  
Author(s):  
C.H. Mandrini ◽  
M.E. Machado ◽  
A.M. Hernandez ◽  
M.G. Rovira
Keyword(s):  
Energy Conversion ◽  
Solar Flares ◽  
Magnetic Energy

Processes of Magnetic-Energy Conversion and Solar Flares

1971 ◽  
Vol 169 ◽  
pp. 379 ◽  
Author(s):  
Bruno Coppi ◽  
Allan B. Friedland
Keyword(s):  
Energy Conversion ◽  
Solar Flares ◽  
Magnetic Energy

scholarly journals Reconnection in substorms and solar flares: analogies and differences

2009 ◽  
Vol 27 (3) ◽  
pp. 1067-1078 ◽  
Author(s):  
J. Birn ◽  
M. Hesse
Keyword(s):  
Magnetic Flux ◽  
Solar Flares ◽  
Energy Transport ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Minor Role ◽  
Magnetospheric Substorms ◽  
Ohmic Dissipation ◽  
Current Sheets ◽  
Poynting Flux

Abstract. Magnetic reconnection is the crucial process in the release of magnetic energy associated with magnetospheric substorms and with solar flares. On the basis of three-dimensional resistive MHD simulations we investigate similarities and differences between the two scenarios. We address in particular mechanisms that lead to the onset of reconnection and energy release, transport, and conversion mechanisms. Analogous processes might exist in the motion of field line footpoints on the sun and in magnetic flux addition to the magnetotail. In both cases such processes might lead to a loss of neighboring equilibrium, characterized by the formation of a very thin embedded current sheet, which acts as trigger for reconnection. We find that Joule (or ohmic) dissipation plays only a minor role in the overall energy transfer associated with reconnection. The dominant transfer of released magnetic energy occurs to electromagnetic energy (Poynting) flux and to thermal energy transport as enthalpy flux. The former dominates in low-beta, specifically initially force-free current sheets expected for the solar corona, while the latter dominates in high-beta current sheets, such as the magnetotail. In both cases the outflow from the reconnection site becomes bursty, i.e. spatially and temporally localized, yet carrying most of the outflow energy. Hence an analogy might exist between bursty bulk flows (BBFs) in the magnetotail and pulses of Poynting flux in solar flares. Further similarities might exist in the role of collapsing magnetic flux tubes, as a consequence of reconnection, in the heating and acceleration of charged particles.

4.13 Magnetic Energy Conversion

2018 ◽  
pp. 573-597
Author(s):  
Ercüment Yüzüak ◽  
Gizem Durak Yüzüak ◽  
İlker Dinçer ◽  
Yalçın Elerman
Keyword(s):  
Energy Conversion ◽  
Magnetic Energy

Plasma Diagnostics of Microflares observed by STIX and AIA

2021 ◽  
Author(s):  
Jonas Saqri ◽  
Astrid Veronig ◽  
Ewan Dickson ◽  
Säm Krucker ◽  
Andrea Francesco Battaglia ◽  
...  
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Emission Measure ◽  
Transport Processes ◽  
X Rays ◽  
Solar Dynamics Observatory ◽  
Energy Bands ◽  
Accurate Analysis ◽  
Great Opportunity ◽  
Wide Range

<p>Solar flares are generally thought to be the impulsive release of magnetic energy giving rise to a wide range of solar phenomena that influence the heliosphere and in some cases even conditions of earth. Part of this liberated energy is used for particle acceleration and to heat up the solar plasma. The Spectrometer/Telescope for Imaging X-rays (STIX) instrument onboard the Solar Orbiter mission launched on February 10th 2020 promises advances in the study of solar flares of various sizes. It is capable of measuring X-ray spectra from 4 to 150 keV with 1 keV resolution binned into 32 energy bins before downlinking. With this energy range and sensitivity, STIX is capable of sampling thermal plasma with temperatures of≳10 MK, and to diagnose the nonthermal bremsstrahlung emission of flare-accelerated electrons. During the spacecraft commissioning phase in the first half of the year 2020, STIX observed 68 microflares. Of this set, 26 events could clearly be identified in at least two energy channels, all of which originated in an active region that was also visible from earth. These events provided a great opportunity to combine the STIX observations with the multi-band EUV imagery from the Atmospheric Imaging Assembly (AIA) instrument on board the earth orbiting Solar Dynamics Observatory (SDO). For the microflares that could be identified in two STIX science energy bands, it was possible to derive the temperature and emission measure (EM) of the flaring plasma assuming an isothermal source. For larger events where more detailed spectra could be derived, a more accurate analysis was performed by fitting the spectra assuming various thermal and nonthermal sources. These results are compared to the diagnostics derived from AIA images. To this aim, the Differential EmissionMeasure (DEM) was reconstructed from AIA observations to infer plasma temperatures and EM in the flaring regions. Combined with the the relative timing between the emission seen by STIX and AIA, this allows us to get deeper insight into the flare energy release and transport processes.</p>

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