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SUMMARY:What is the real size of the magnetosphere of an accreting star?
DTSTART:20261027T060000Z
DTEND:20261027T070000Z
DTSTAMP:20261017T123300Z
UID:indico-event-5379@indico-tdli.sjtu.edu.cn
DESCRIPTION:Speakers: Nazar Ikhsanov (Pulkovo Observatory)\n\nHost: Dong 
 LaiJoin Tencent Meeting：https://meeting.tencent.com/dm/zWcIwnIuoiQ3Meeti
 ng ID: 300682415 (no password）Abstract:The methods to evaluate the size 
 of the magnetosphere of an accreting star are discussed. I emphasize that 
 there is no reliable way to accurately determine the parameters of the acc
 retion flow on the basis of currently available observational data. This i
 ntroduces uncertainty into the equation describing the balance between the
  pressure of the accretion flow and the pressure of the stellar magnetic f
 ield at the magnetospheric boundary\, rendering it incomplete. As an alter
 native\, we propose to focus on the continuity equation for the accretion 
 flow at the magnetospheric boundary. This opens a new approach to the magn
 etospheric accretion in which the radius of the magnetosphere is defined a
 s a minimum possible distance from the center of the accreting star to the
  point at which the accretion flow enters the stellar magnetic field at a 
 rate which equals to the mass accretion rate onto the stellar surface. We 
 evaluate the size of the magnetosphere following this approach for a situa
 tion in which the entry of the accreting gas into the stellar field is gov
 erned by Bohm diffusion. The magnetospheric radius evaluated for this case
  appears to be significantly smaller than the conventionally accepted valu
 e of the equilibrium radius for a spherical accretion flow\, known as the 
 Alfven radius. We show that the obtained new expression for the radius of 
 the magnetosphere allows us to solve many puzzling problems on the origin 
 and evolution of accretion-powered degenerate stars in close binary system
 s. Biography:Nazar Ikhsanov is the Director of the Central Astronomical Ob
 servatory of the Russian Academy of Sciences at Pulkovo (Pulkovo Observato
 ry\, Saint-Petersburg\, Russia). MS (the Leningrad State University in 198
 6) and PhD (the Pulkovo Observatory in 1989). Career milestones: an Alexan
 der von Humboldt Fellow at the Ludwig-Maximilian University (Munich\, Germ
 any) and at the Max Planck Institute for Radioastronomy (Bonn\, Germany)\;
  a Research Fellow at the Korea Astronomy and Space Science Institute (Dae
 jeon\, South Korea)\; Maria Curie Fellow at the Institute of Astronomy of 
 the University of Cambridge (Cambridge\, UK)\; NPP Program Senior Fellow a
 t the Marshal Space Flight Center (Huntsville\, AL\, US). In 2011-2016 is 
 a Head of the Stellar Evolution Dept. of Pulkovo Observatory and a Profess
 or of Astronomy of the Saint-Petersburg State University. From 2016 is the
  Director of Pulkovo Observatory. Main topics of research are magneto-rota
 tional evolution of degenerate stars\, accretion in close binaries and AGN
 s and flaring activity of astrophysical objects.\n\nhttps://indico-tdli.sj
 tu.edu.cn/event/5379/
LOCATION:Tsung-Dao Lee Institute/S4F-SW - Open Area (Tsung-Dao Lee Institu
 te)
URL:https://indico-tdli.sjtu.edu.cn/event/5379/
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