Continuous Plasma Outflows from the Edge of a Solar Active Region as a Possible Source of Solar Wind

Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku, J.; Bando, T.; DeLuca, E. E.; Lundquist, L. L.; Tsuneta, S.; Harra, L. K.; Katsukawa, Y.; Kubo, Masahito; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masataka; Bookbinder, Jay A.; Golub, L.; Korreck, K. E.; Su, Yingna; Shibasaki, Κ.; Shimizu, Toshifumi; Nakatani, Ichiro

doi:10.1126/science.1147292

Cited by 207 publications

(178 citation statements)

References 19 publications

Supporting

Mentioning

163

Contrasting

Order By: Relevance

“…Outflows with a projected speed of 140 km s −1 near an AR were also detected by Sakao et al (2007) based on observations from XRT/Hinode in soft X-rays. These authors claimed that continuous outflow does exist, a notion based on the appearance of the very frequent outward propagation of intensity enhancements in the X-ray movie.…”

Section: Introductionmentioning

confidence: 99%

“…During solar minimum, the fast solar wind is recognized to originate in the (polar) coronal holes (CHs), in particular from the magnetic funnels according to both observations (Xia et al 2003;Tu et al 2005a,b;Marsch et al 2006;Tian et al 2010) and theoretical models Hackenberg et al 2000;Esser et al 2005;He et al 2008). The slow solar wind has several possible source regions, such as the boundaries of polar CHs (Wang et al 1990), the helmet streamers , the funnel-like structures in the quiet regions (He et al 2007;Tian et al 2008aTian et al , 2009, and the edges of active regions (ARs) (e.g., Sakao et al 2007;Harra et al 2008). For a comprehensive review of previous studies of plasma characteristics and magnetic features in the solar wind source regions, we refer to Marsch (2006).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

He¹,

Marsch²,

Tu³

et al. 2010

A&A

View full text Add to dashboard Cite

Context. It has already been established that the solar wind may originate at the edges of active regions (ARs), but the key questions of how frequently these outflows occur, and at which height the nascent solar wind originates have not yet been addressed. Aims. We study the occurrence rate of these intermittent outflows, the related plasma activities beneath in the low solar atmosphere, and the interplanetary counterparts of the nascent solar wind outflow. Methods. We use the observations from XRT/Hinode and TRACE to study the outflow patterns. The occurrence frequency of the intermittent outflow is estimated by counting the occurrences of propagating intensity enhancements in height-time diagrams. We adopt observations of SOT/Hinode and EIS/Hinode to investigate the phenomena in the chromosphere associated with the coronal outflows. The ACE plasma and field in-situ measurements near Earth are used to study the interplanetary manifestations. Results. We find that in one elongated coronal emission structure, referred to as strand, the plasma flows outward intermittently, about every 20 min. The flow speed sometimes exceeds 200 km s −1 , which is indicative of rapid acceleration, and thus exceeds the coronal sound speed at low altitudes. The inferred flow speed of the soft-X-ray-emitting plasma component seems a little higher than that of the Fe ix/x-emitting plasma component. Chromospheric jets are found to occur at the root of the strand. Upflows in the chromosphere are also confirmed by blue-shifts of the He ii line. The heliospheric plasma counterpart close to the Earth is found to be an intermediate-speed solar wind stream. The AR edge may also deliver some plasmas to a fraction of the fast solar wind stream, most of which emanate from the neighboring CH. Conclusions. The possible origin of the nascent solar wind in the chromosphere, the observed excessive outflow speed of over 200 km s −1 in the lower corona, and the corresponding intermediate-speed solar wind stream in interplanetary space are all linked in our case study. These phenomena from the low solar atmosphere to the heliosphere near Earth in combination shed new light on the solar wind formation process. These observational results will constrain future modeling of the solar winds originating close to an AR.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

He¹,

Marsch²,

Tu³

et al. 2010

A&A

View full text Add to dashboard Cite

show abstract

“…For instance, at the edges of ARs, outflows have often been observed with velocities of tens of km s −1 . This has actually been proposed to be important for the solar wind Brekke et al (1997), Winebarger et al (2001), Sakao et al (2007). Such flows might arise from the reconnection between small-scale emerging fields and larger-scale open field lines of ARs (Liu and Su 2014).…”

Section: Temporal Evolution Of Active-region Magnetic Fieldsmentioning

confidence: 99%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

176

125

View full text Add to dashboard Cite

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

show abstract

“…Electron densities in the outflow region of 7 × 10 8 cm −3 derived from a density sensitive intensity ratio of Fe xii lines by Doschek et al (2008) and ≈ 3.2×10 9 cm −3 estimated by Sakao et al (2007) are rather low for an active region. Similarly, the outflow regions have little radiance in contrast to active regions (Del Zanna, 2008;Harra et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Outflows at the Edges of an Active Region in a Coronal Hole: A Signature of Active Region Expansion?

et al. 2009

View full text Add to dashboard Cite

Outflows of plasma at the edges of active regions surrounded by quiet Sun are now a common observation with the Hinode satellite. While there is observational evidence to suggest that the outflows are originating in the magnetic field surrounding the active regions, there is no conclusive evidence that reveals how they are driven. Motivated by observations of outflows at the periphery of a mature active region embedded in a coronal hole, we have used a three-dimensional simulation to emulate the active region's development in order to investigate the origin and driver of these outflows. We find outflows are accelerated from a site in the coronal hole magnetic field immediately surrounding the active region and are channelled along the coronal hole field as they rise through the atmosphere. The plasma is accelerated simply as a result of the active region expanding horizontally as it develops. Many of the characteristics of the outflows generated in the simulation are consistent with those of observed outflows: velocities up to 45 km s −1 , properties akin to the coronal hole, proximity to the active region's draining loops, expansion with height, and projection over monopolar photospheric magnetic concentrations. Although the horizontal expansion occurs as a consequence of the active region's development in the simulation, expansion is also a general feature of established active regions. Hence, it is entirely possible and plausible that the expansion acceleration mechanism displayed in the simulation is occurring in active regions on the Sun and, in addition to reconnection, is driving the outflows observed at their edges.

show abstract

Continuous Plasma Outflows from the Edge of a Solar Active Region as a Possible Source of Solar Wind

Cited by 207 publications

References 19 publications

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

The magnetic field in the solar atmosphere

Outflows at the Edges of an Active Region in a Coronal Hole: A Signature of Active Region Expansion?

Contact Info

Product

Resources

About