Abstract
We present a study of the outflow velocity of the fast wind in the northern polar coronal hole observed on 21 May 1996, during the minimum of solar activity, in the frame of a joint observing program of the SOHO (Solar Heliospheric Observatory) mission. The outflow velocity is inferred from an analysis of the Doppler dimming of the intensities of the O vi λ1032, 1037 and H i Lα λ1216 lines observed between 1.5 R ⊙ and 3.5 R ⊙ with the Ultraviolet Coronagraph Spectrometer (UVCS), operating onboard SOHO. The analysis shows that for a coronal plasma characterized by low density, as derived for a polar hole at solar minimum by Guhathakurta et al. (1999), and low temperature, as directly measured at the base of this coronal hole by David et al. (1998), the oxygen outflow speed derived spectroscopically is consistent with that implied by the proton flux conservation. The hydrogen outflow is also consistent with flux conservation if the deviation from isotropy of the velocity distribution of the hydrogen atoms is negligible. Hence, for this cool and tenuous corona, the oxygen ions and neutral hydrogen atoms flow outward roughly at the same speed, which increases from 40 km s−1 at 1.5 R ⊙ to 360 km s−1 at 3.1 R ⊙, with an average acceleration of the order of ∼4.5×103 cm s−2. The highly anisotropic velocity distributions of the O vi ions found in the analysis confirm that the process which is heating the oxygen ions acts preferentially across the magnetic field.
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Antonucci, E.: 1998, Proceedings Crossroads for European Solar and Heliospheric Physics, ESA SP–417, p. 25.
Antonucci, E.: 1999, Proceedings 8th SOHO Workshop ‘Plasma Dynamics and Diagnostics in the Solar Transition Region and Corona’, ESA SP–446, p. 53.
Antonucci, E., Giordano, S. and Dodero, M. A.: 2000, Adv. Space Res. 25, 1923.
Antonucci, E., Noci, G., Kohl, J. L., Tondello, G., Huber, M. C. E., Giordano, S., Benna, C., Ciaravella, A., Fineschi, S., Gardner, L. D., Martin, R., Michels, J., Naletto, G., Nicolosi, P., Panasyuk, A., Raymond, J. C., Romoli, M., Spadaro, D., Strachan, L., and Van Ballegooijen, A. A.: 1997a, Astron. Soc. Pacific Conf. Series 118, 273.
Antonucci, E., Giordano, S., Benna, C., Kohl, J. L., Noci, G., Michels, J. and Fineschi, S.: 1997b, 5th SOHO Workshop, ESA SP–404, p. 175.
Beckers, J.M., and Chipman, E.: 1974, Solar Phys. 34, 151.
Corti, G., Poletto G., Romoli, M., Michels, J., Kohl, J. L., and Noci, G.: 1997, 5th SOHO Workshop, ESA SP–404, p. 289.
Cranmer, S. R.: 1998, Astrophys. J. 508, 925.
Cranmer, S. R., Kohl, J. L., Noci, G., Antonucci, E., Tondello, G., Huber, M. C. E., Strachan, L., Panasyuk, A., Gardner, L. D., Romoli, M., Fineschi, S., Dobrzycka, D., Raymond, J. C., Nicolosi, P., Siegmund, O. H. W., Spadaro, D., Benna, C., Ciaravella, A., Giordano, S., Habbal, S. R., Karovska, M., Li, X., Martin, R., Michels, J. G., Modigliani, A., Naletto, G., O'Neal, R. H., Pernechele, C., Poletto, G., Smith, P. L., and Suleiman, R. M.: 1999, Astrophys. J. 511, 481.
David, C., Gabriel, A. H., and Bely-Dubau F.: 1997, 5th SOHO Workshop, ESA SP–404, p. 319.
David, C., Gabriel, A. H., Bely-Dubau F., Fludra, A., Lemaire, P., and Wilhelm, K.: 1998, Astron. Astrophys. 336, L90.
Dobrzycka, D., Cranmer, S. R., Panasyuk, A. V., Strachan, L., and Kohl, J. L.: 1999, J. Geophys. Res. 104, A5, 9791.
Dodero, M. A., Antonucci, E., Giordano, S., and Martin, R.: 1998, Solar Physics 183, 77.
Esser, E., Fineschi, S., Dobrzycka, D., Habbal, S. R., Edgar, R. J., Raymond, J. C., Kohl, J. L., and Guhathakurta, M.: 1999, Astrophys. J. 510, L63.
Fisher, R. and Guhathakurta, M.: 1995, Astrophys. J. 447, L139.
Gardner, L. D., Kohl, J. L, Daigneau, P. S., Dennis, E. F., Fineschi, S., Michels, J., Nystrom, G. U., Panasyuk, A., Raymond, J. C., Reisenfeld, D. J., Smith, P. L., Strachan, L., Suleiman, R., Noci, G., Romoli, M., Ciaravella, A., Modigliani, A., Huber, M. C. E., Antonucci, E., Benna, C., Giordano, S., Tondello, G., Nicolosi, P., Naletto, G., Pernechele, C., Spadaro, D., Siegmund, O. H. W., Allegra, A., Carosso, P., and Jhabvala, M.: 1996, Proc. SPIE 2831, 2.
Giordano, S.: 1999, Ph.D Thesis, Università di Torino.
Giordano, S., Antonucci, E., and Dodero, M. A.: 2000, Adv. Space Res. 25, 1927.
Giordano, S., Antonucci, E., Benna, C., Kohl, J. L., Noci, G., Michels, J., and Fineschi, S.: 1997, 'Correlated Phenomena at the Sun, in Heliosphere and in Geospace, ESA SP–415, p. 327.
Giordano, S., Antonucci, E., Noci, G., Romoli, M., and Kohl, J. L.: 2000, Astrophys. J. 531, L79.
Goldstein, B. E. et al.: 1996, Astron. Astrophys. 316, 293.
Grall, R. R. et al.: 1996, Nature 379, 429.
Guhathakurta, M., Fludra, A., Gibson, S. E., Biesecker, D., and Fisher, R.: 1999, J. Geophys. Res. 104(A5), 9801.
Habbal, S. R., Woo, R., Fineschi, S., O'Neal, R., Kohl, J. L., Noci, G., and Korendyke, C.: 1997, Astrophys. J. 489, L103.
Hyder, C. L. and Lites, B. W.: 1970, Solar Phys. 14, 147.
Ko, Y.–K., Fisk, L. A., Geiss, J., Gloeckler, G., and Guhathakurta, M.: 1997, Solar Phys. 171, 345.
Kohl, J. L. and Withbroe, G. L.: 1982, Astrophys. J. 256, 263.
Kohl, J. L., Esser, R., Gardner, L. D., Habbal, S., Daigneau, P. S., Dennis, E. F., Nystrom, G. U., Panasyuk, A., Raymond, J. C., Smith, P. L., Strachan, L., van Ballegooijen, A. A., Noci, G., Fineschi, S., Romoli, M., Ciaravella, A., Modigliani, A., Huber, M. C. E., Antonucci, E., Benna, C., Giordano, S., Tondello, G., Nicolosi, P., Naletto, G., Pernechele, C., Spadaro, D., Poletto, G., Livi, S., von der Lühe, O., Geiss, J., Timothy, J. G., Gloecker, G., Allegra, A., Basile, G., Brusa, R., Wood, B., Siegmund, O. H. W., Fowler, W., Fisher, R., and Jhabvala, M.: 1995, Solar Phys. 162, 313.
Kohl, J. L., Noci, G., Antonucci, E., Tondello, G., Huber, M. C. E., Gardner, L. D., Nicolosi, P., Strachan, L., Fineschi, S., Raymond, J. C., Romoli, M., Spadaro, D., Panasyuk, A., Siegmund, O. H. W., Benna, C., Ciaravella, A., Cranmer, S. R., Giordano, S., Karovska, M., Martin, R., Michels, J., Modigliani, A., Naletto, G., Pernechele, C., Poletto, G., and Smith, P.L.: 1997, Solar Phys. 175, 613.
Kohl, J. L., Noci, G., Antonucci, E., Tondello, G., Huber, M. C. E., Cranmer, S. R., Strachan, L., Panasyuk, A. V., Gardner, L. D., Romoli, M., Fineschi, S., Dobrzycka, D., Raymond, J. C., Nicolosi, P., Siegmund, O. H. W., Spadaro, D., Benna, C., Ciaravella, A., Giordano, S., Habbal, S. R., Karovska, M., Li, X., Martin, R., Michels, J. G., Modigliani, A., Naletto, G., O'Neal, R. H., Pernechele, C., Poletto, G., Smith, P. L., and Suleiman, R. M.: 1998, Astrophys. J. 501, L127.
Kopp, R. A. and Holzer, T. E.: 1976, Solar Physics 49, 43.
Lemaire, P., Emerich, C., Curdt, W., Schülhe, U., and Wilhelm, K.: 1998, Astron. Astrophys. 334, 1095.
Li, X., Habbal, S. R., Kohl, J. L., and Noci, G.: 1998, Astrophys. J. 501, L133.
McComas, D. J., Bame, S. J., Barraclough, B. L., Feldman, W. C., Funsten, H. O., Gosling, J. T., Riley, P., Skoug, R., Balogh, A., Forsyth, R., Goldstein, B. E., and Neugebauer, M.: 1998, Geophys. Res. Lett. 25, 1.
Munro, R. H. and Jackson, B. V.: 1977, Astrophys. J. 213, 874.
Noci G., Kohl, J. L., and Withbroe, G. L.: 1987, Astrophys. J. 315, 706.
Noci, G., Kohl, J. L., Antonucci, E., Tondello, G., Huber, M. C. E., Fineschi, S., Gardner, L. D., Naletto, G., Nicolosi, P., Raymond, J. C., Romoli, M., Spadaro, D., Siegmund, O. H. W., Benna, C., Ciaravella, A., Giordano, S., Michels, J., Modigliani, A., Panasyuk, A., Pernechele, C., Poletto, G., Smith, P. L., and Strachan, L.: 1997, Adv. Space Res. 20, 2219.
Phillips, J. L., Bame, S. J., Barnes, A., Barraclough, B. L., Feldman, W. C., Goldstein, B. E., Gosling, J. T., Hoogeveen, G.W., McComas, D. J., Neugebauer, M., and Suess, S. T.: 1995 Geophys. Res. Lett. 22, 3301.
Strachan, L., Kohl, J. L., Weiser, H., Withbroe, G. L., and Munro, R. H.: 1993. Astrophys. J. 412, 410.
Wilhelm, K., Marsch, E., Dwivedi, B. N., Hassler, D.M., Lemaire, P., Gabriel, A. H., and Huber, M.: 1998, Astrophys. J. 500, 1023.
Withbroe, G. L., Kohl, J. L., Weiser, H. and Munro, R. H.: 1982, Space. Sci. Rev. 33, 17.
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Antonucci, E., Dodero, M.A. & Giordano, S. Fast Solar Wind Velocity in a Polar Coronal Hole during Solar Minimum. Solar Physics 197, 115–134 (2000). https://doi.org/10.1023/A:1026568912809
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DOI: https://doi.org/10.1023/A:1026568912809