ORIGIN OF THE SLOW SOLAR WIND K. Fujiki ， T. Ohmi, M. Kojima, M. Tokumaru Solar-Terrestrial Environment Laboratory, Nagoya University and K. Hakamada Department of Engineering Physics, Chubu University

Slow solar wind from a small equatorial coronal hole Slow solar wind from a polar coronal hole

Intermediate and slow streams originated not in smaller coronal holes at low latitudes and from open field regions just outside coronal hole boundaries. [Neugebauer et al., 1998] The speed of the solar wind scales with the coronal hole area. [Nolte et al., 1976] Relation between speed and coronal hole area

Wang & Sheely model RADIAL DISTANCE Magnetic field configuration smaller expansion larger expansion high speed low speed

Slow SW from an equatorial small CH

Solar Wind Structure at Solar Minimum slower solar wind

Carrington Rotations The slower wind originates from the vicinity of active regions August 6 – October 17, 1995

Carrington Rotations The slower wind also originates from the vicinity of active regions April 19 – July 10, 1995

CR1897 HPS slow wind slow wind from seCH fast wind

10 6 K CR1897 HPS slow wind slow wind from seCH fast wind

CR1897 HPS slow wind slow wind from seCH fast wind

Parameter Slow ( HPS ) Slower ( seCH ) Fast ( leCH ) V P [km/s] 343±12 323±9 673±14 N P [cm -3 ] 11.7± ± ±0.5 T P [10 5 K] 0.39± ± ±0.39 T O [10 6 K] 1.85± ± ±0.13 N α / N P 0.009± ± ±0.004 Solar Wind in CR 1897 (June 12 – July 10, 1995)

Parameter Slow ( HPS ) Slow ( seCH ) Fast ( leCH ) V P [km/s] 343±12 323±9 673±14 N P [cm -3 ] 11.7± ± ±0.5 T P [10 5 K] 0.39± ± ±0.39 T O [10 6 K] 1.85± ± ±0.13 N α / N P 0.009± ± ±0.004

fast windslow wind (HPS) Sourcecoronal holehelmet N variancesteadyvariable Na/Nplargesmall slow wind (SCH) coronal hole steady large

Slow SW from a polar CH

Polar Low-speed Solar Wind at Solar Activity Maximum of Cycle 22 Ohmi et al. [2001] June 27, 1990

Polar Low-speed Solar Wind at Solar Activity Maximum of Cycle 23 Ohmi et al. [2002] October 23, 1999

Small Polar Coronal Hole

Conclusions In addition to the slow solar wind from helmet streamer, the slow solar wind originates from small coronal holes. slow slower fast Wang and Sheely model of inverse correlation between velocity and expansion factor seems to explain these slower solar winds.

Magnetic Field in the Coronal Holes high latitude CH 12 G Fast wind small polar CH 4 ～ 6 G Slow windlarge flux expansion & less magnetic energy small equatorial CH 18 G Slow windlarge flux expansion & large magnetic energy Is it really possible to explain same acceleration mechanism? Photospheric Condition is significantly different.

Required More in situ observations of the slow stream from small coronal holes. ･･･ is difficult to observe the polar wind. Physical properties of density, acceleration profile, and temperature in corona of the slow streams. ･･･ can be observed by SOLAR- B.(EIS/XRT)

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