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The global return current in a pulsar's magnetosphere
New Astronomy 47 (2016) 1–2
Contents lists available at ScienceDirect
New Astronomy journal homepage: www.elsevier.com/locate/newast
The global return current in a pulsar’s magnetosphere Yudith Barzilay∗ P.O. Box 219, Lehavim 8533800, Israel
a r t i c l e
i n f o
Article history: Received 16 December 2015 Revised 21 December 2015 Accepted 22 December 2015 Available online 5 January 2016
a b s t r a c t An open issue in pulsar’s models is the current adjustment between the gap current and the global current that depends on the global structure of the pulsar’s magnetosphere. Here I propose a mechanism for the global return current in pulsars. © 2016 Elsevier B.V. All rights reserved.
Communicated by E.P.J van den Heuvel Keywords: Astroparticle physics Acceleration of particles Stars: pulsars: individual (return current) (Stars:) pulsars: general Stars: magnetic field Stars: rotation
1. Introduction Models of pulsar activity are associated with an electron– positron pair production cascade. One of the basic models for pulsar activity is an electron beam extracted freely from the star surface above the polar cap region. The electrons are accelerating along the open field lines to high Lorentz factor (106 –107 ) needed to initiate pair production (Barzilay, 2011; Arons and Scharlemann, 1979; Muslimov and Tsygan, 1992; Muslimov and Harding, 1997). In a continuation of the work of Barzilay (2011), taking into account a simple model of pair production, I get a small returning flux of positrons along the open field lines above the pulsar polar cap. This is compatible with the results of Muslimov and Harding (2002). These results along with the full model will be reported in a separate paper.
2. The model In this model for pulsar activity the electrons are extracted freely from the star surface above the polar cap region. However, it is not clear how the star can supply all the needed electrons. An open issue is the current adjustment between the gap current and the global current that depends on the global structure of the
∗
Tel.: +972 507732348; fax: +972 86513976. E-mail address: [email protected]
http://dx.doi.org/10.1016/j.newast.2015.12.010 1384-1076/© 2016 Elsevier B.V. All rights reserved.
pulsar’s magnetosphere. I propose a well-known mechanism (also not completely understood) for the global return current: lightning. On Earth, there are three primary types of lightning: from a cloud to itself (intra-cloud or IC), from one cloud to another cloud (cloud-cloud or CC) and between a cloud and the ground (cloudground or CG). Today there are satellites monitoring lightning frequency, and it is accepted that the global lightning flash frequency on earth is on the order of 40 flashes per second, with CG lightning flashes some less than 25% of all total lightning flashes worldwide (Annual Lightning Flash Rate, 2013; NASA Dataset Information, 2007). The lightning phenomenon is not unique to earth. Lightning has been observed within the atmospheres of other planets, such as Jupiter, Saturn, Uranus, Neptune and potentially at Venus (Fischer et al., 2011). There are no longer nuclear fusion processes in a pulsar or neutron star. These objects are assumed to have an atmosphere of few centimeters, and the star’s surface is rigid. Due to the pair cascade the magnetosphere is filled with electron–positron plasma. Lightning could be a very efficient mechanism for current adjustment, occurring all over the star. The lightning can account for the global return current mechanism in pulsars. 3. Discussion and conclusions A pulsar’s magnetosphere is filled with electron–positron plasma. Lightning could be a very efficient mechanism for current and charge adjustment, occurring all over the star. It can account for the global return current mechanism in pulsars.
2
Y. Barzilay / New Astronomy 47 (2016) 1–2
Acknowledgment The author thank the anonymous referee for the comments that helped improve this manuscript. References Annual Lightning Flash Rate, 2013. National Oceanic and Atmospheric Administration, http://www.sos.noaa.gov/Datasets/dataset.php?id=6 Arons, J., Scharlemann, E.T., 1979. ApJ 231, 854. Barzilay, Yudith, 2011. ApJ 732, 123.
Fischer, Georg, Gurnett, D.A., Yair, Yoav, 2011. Extraterrestrial lightning and its past and future investigation. In: Wood, M.D. (Ed.), Lightning: Properties, Formation and Type. Nova Science Publishers, pp. 19–38. Muslimov, A.G., Harding, A.K., 1997. ApJ 485, 735. Muslimov, A.G., Harding, A.K., 2002. ApJ 568, 862. Muslimov, A.G., Tsygan, A.I., 1992. MNRAS 255, 61. NASA Dataset Information, 2007 (September 11, 2007), http://thunder.msfc.nasa.gov/ data/.
Contents lists available at ScienceDirect
New Astronomy journal homepage: www.elsevier.com/locate/newast
The global return current in a pulsar’s magnetosphere Yudith Barzilay∗ P.O. Box 219, Lehavim 8533800, Israel
a r t i c l e
i n f o
Article history: Received 16 December 2015 Revised 21 December 2015 Accepted 22 December 2015 Available online 5 January 2016
a b s t r a c t An open issue in pulsar’s models is the current adjustment between the gap current and the global current that depends on the global structure of the pulsar’s magnetosphere. Here I propose a mechanism for the global return current in pulsars. © 2016 Elsevier B.V. All rights reserved.
Communicated by E.P.J van den Heuvel Keywords: Astroparticle physics Acceleration of particles Stars: pulsars: individual (return current) (Stars:) pulsars: general Stars: magnetic field Stars: rotation
1. Introduction Models of pulsar activity are associated with an electron– positron pair production cascade. One of the basic models for pulsar activity is an electron beam extracted freely from the star surface above the polar cap region. The electrons are accelerating along the open field lines to high Lorentz factor (106 –107 ) needed to initiate pair production (Barzilay, 2011; Arons and Scharlemann, 1979; Muslimov and Tsygan, 1992; Muslimov and Harding, 1997). In a continuation of the work of Barzilay (2011), taking into account a simple model of pair production, I get a small returning flux of positrons along the open field lines above the pulsar polar cap. This is compatible with the results of Muslimov and Harding (2002). These results along with the full model will be reported in a separate paper.
2. The model In this model for pulsar activity the electrons are extracted freely from the star surface above the polar cap region. However, it is not clear how the star can supply all the needed electrons. An open issue is the current adjustment between the gap current and the global current that depends on the global structure of the
∗
Tel.: +972 507732348; fax: +972 86513976. E-mail address: [email protected]
http://dx.doi.org/10.1016/j.newast.2015.12.010 1384-1076/© 2016 Elsevier B.V. All rights reserved.
pulsar’s magnetosphere. I propose a well-known mechanism (also not completely understood) for the global return current: lightning. On Earth, there are three primary types of lightning: from a cloud to itself (intra-cloud or IC), from one cloud to another cloud (cloud-cloud or CC) and between a cloud and the ground (cloudground or CG). Today there are satellites monitoring lightning frequency, and it is accepted that the global lightning flash frequency on earth is on the order of 40 flashes per second, with CG lightning flashes some less than 25% of all total lightning flashes worldwide (Annual Lightning Flash Rate, 2013; NASA Dataset Information, 2007). The lightning phenomenon is not unique to earth. Lightning has been observed within the atmospheres of other planets, such as Jupiter, Saturn, Uranus, Neptune and potentially at Venus (Fischer et al., 2011). There are no longer nuclear fusion processes in a pulsar or neutron star. These objects are assumed to have an atmosphere of few centimeters, and the star’s surface is rigid. Due to the pair cascade the magnetosphere is filled with electron–positron plasma. Lightning could be a very efficient mechanism for current adjustment, occurring all over the star. The lightning can account for the global return current mechanism in pulsars. 3. Discussion and conclusions A pulsar’s magnetosphere is filled with electron–positron plasma. Lightning could be a very efficient mechanism for current and charge adjustment, occurring all over the star. It can account for the global return current mechanism in pulsars.
2
Y. Barzilay / New Astronomy 47 (2016) 1–2
Acknowledgment The author thank the anonymous referee for the comments that helped improve this manuscript. References Annual Lightning Flash Rate, 2013. National Oceanic and Atmospheric Administration, http://www.sos.noaa.gov/Datasets/dataset.php?id=6 Arons, J., Scharlemann, E.T., 1979. ApJ 231, 854. Barzilay, Yudith, 2011. ApJ 732, 123.
Fischer, Georg, Gurnett, D.A., Yair, Yoav, 2011. Extraterrestrial lightning and its past and future investigation. In: Wood, M.D. (Ed.), Lightning: Properties, Formation and Type. Nova Science Publishers, pp. 19–38. Muslimov, A.G., Harding, A.K., 1997. ApJ 485, 735. Muslimov, A.G., Harding, A.K., 2002. ApJ 568, 862. Muslimov, A.G., Tsygan, A.I., 1992. MNRAS 255, 61. NASA Dataset Information, 2007 (September 11, 2007), http://thunder.msfc.nasa.gov/ data/.