Dependence of anomalous resistivity on bulk drift velocity of electrons in the reconnecting current sheets in solar flares

• Published in: Research in astronomy and astrophysics Vol. 10; no. 11; pp. 1186 - 1194
• Main Authors: Wu, Gui-Ping, Huang, Guang-Li, Ji, Hai-Sheng
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.11.2010; Department of Physics,Southeast University,Nanjing 210096,China%Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China
• Subjects: 依赖性; 太阳耀斑; 电流片; 电阻率异常; 离子漂移速度; waves; Sun: flares; instabilities; acceleration of particles
• ISSN: 1674-4527; 2397-6209
• DOI: 10.1088/1674-4527/10/11/009

Abstract Anomalous resistivity is critical for triggering fast magnetic reconnection in the nearly collisionless coronal plasma. Its nonlinear dependence on bulk drift velocity is usually assumed in MHD simulations. However, the mechanism for the production of anomalous resistivity and its evolution is still an open question. We numerically solved the one dimension Vlasov equation with the typical solar coronal parameters and realistic mass ratios to infer the relationship between anomalous resistivity and bulk drift velocity of electrons in the reconnecting current sheets as well as its non- linear characteristics. Our principal findings are summarized as follows： 1） the relationship between the anomalous resistivity and bulk drift velocity of electrons relative to ions may be described as ηmax=0.03724（vd/ve）^5.702Ωm for vd/ve in the range of 1.4-2.0 and ηmax=0.8746（vd/ve）^1.284Ωm for vd/ve in the range of 2.5-4.5;2）if drift velocity is just slightly larger than the threshold of ion-acoustic instability, the anomalous resistivity due to the wave-particle interactions is enhanced by about five orders as compared with classic resistivity due to Coulomb collisions, With the increase of drift velocity from 1.4ve to 4.5Ve, the anomalous resistivity continues to increase 100 times; 3） in the rise phase of unstable waves, the anomalous resistivity has the same order as the one estimated from quasi-linear theory; after saturation of unstable waves, the anomalous resistivity decreases at least about one order as com- pared with its peak value; 4） considering that the final velocity of electrons ejected out of the reconnecting current sheet （RCS） decreases with the distance from the neutral point in the neutral plane, the anomalous resistivity decreases with the distance from the neutral point, which is favorable for the Petschek-like reconnection to take place.