Observation of aurora at South Pole Station: A past, present and future perspective

Transcription

1 Observation of aurora at South Pole Station: A past, present and future perspective NIPR symposium on conjugate aurora and SuperDARN past, present and future Feb 16 17, 2012 Yusuke Ebihara RISH, Kyoto University, Japan Acknowledgments: Profs. Masaki Ejiri, Sho Ichi Okano, Allan T. Weatherwax, Nelson C. Maynard, Drs. Masaki Okada, Shu Takeshita, Akira Kadokura, Toshio Motoba, Ryuho Kataoka, Yasumasa Tanaka, Satoko Saita (Takasaki), Shin Suzuki, Masaki Tsutsumi, Akira S. Yukimatu, Sonia Figueiredo, Steve E. Millan, and Zejun Hu

2 2 The United States South Pole Station US s South Pole Station South Pole 3 rd generation of station facility The United States South Pole Station is located very closed to geographic south pole ( S in 2007).

3 3 Why South Pole Station? Geographic latitude of 90 S. Astronomical twilight lasts for 4.5 months. Auroras are observable for 4.5 months continuously (if there is no cloud.) Geomagnetic latitude of 74 deg. Various types of auroras, including dayside/nightside auroras, are observable. Well facilitated infrastructure. Stable power supply. All data are transferred from South Pole to Japan with a delay of a few days.

4 Japan s contribution to auroral observation at South Pole 4 FY 1996 The project was initiated by Prof. Ejiri. All sky imager was designed by Prof. Okano, and installed by Prof. Okano and Dr. Okada under Agreement of Cooperation between NSF and NIPR. FY 2005 All sky imager retreated. FY 2007 Proposal was approved by NSF. All sky imager was re installed at new building. (PI: Prof. Weatherwax, Siena College, USA. Ebihara is a collaborator of this proposal.) FY nd all sky imager was installed. FY rd all sky (panchromatic) imager was installed by Drs. Kadokura and Motoba.

5 5 My contribution to auroral observation at South Pole FY 2001: Re installation of ASI 1 FY 2002: Maintenance and data collection FY 2004: Maintenance and data collection FY 2005: Retreat (shipped to Longyearbyen directly) FY 2007: Re installation of ASI 1 FY 2008: Installation of dehumidifiers FY 2009: Installation of ASI 2 FY 2010: Maintenance and data collection

6 6 Recent advances of 2001 Latest Instruments One imager Photo by Dr. Kadokura Three imagers

7 7 Recent advances of 2001 Latest Accommodation One single bed and curtain Bed, desk, shelf, chair, door, telephone and Internet connection Flight Not so comfortable cabin in C 141. Comfortable cabin in C 17. We can walk along an aisle without saying excuse me.

8 8 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

9 9 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

10 Quasi stationary auroral patches (Ebihara et al., 2007, JGR) 10 MLT UT 3.5 Faint (~1 kr), quasi stationary auroral patches were observed in the morningnoon sector. Poleward Tanaka et al. (2011, JpGU) suggest that the electric fields associated with field line resonance can account for both the oscillation of patches and the poleward moving arcs reasonably. They are not pulsating. They are visible for, at least, a few hours. Similar patches were observed in Akaska in sub auroral region on nightside (Kubota et al., 2003, GRL) They show oscillation in azimuth with a period of ~5 minutes. Similar oscillation was observed in Canada (Oguti et al., 1987) Poleward moving arcs are overlaid in conjunction with the oscillation. Similar poleward moving arcs were observed (Millan et al., 1999; Kozlovsky et al., 2002)

11 11 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

12 12 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

13 Evolution of discrete arc (Figueiredo et al., 2005, AG) 13 Surge horn Auroral image from DMSP Midnight Cluster 1 Cluster 2 Cluster Cluster 4 ~0.5 km/s Dusk Noon Dawn ASI at South Pole Station observed a surge horn during the expansion phase of a moderate substorm. The surge horn moved poleward with 0.5 km/s. At the same time, Cluster satellites traversed the surge horn at 4.5 Re altitude.

14 Evolution of discrete arc (Figueiredo et al., 2005, AG) 14 Downgoing electrons Plasma sheet The region of plasma sheet Perpendicular potential Cluster 4 Cluster 2 Cluster 1 ~0.5 km/s Electric field Field aligned current Equatorward Fundamental features are consistent with Fujii et al. (1994) Cluster Re altitude Cluster satellites observed the most intense E field and FAC at the poleward boundary of the plasma sheet. The region of the plasma sheet moved poleward with a speed of ~0.5 km/s, which is consistent with that of the poleward moving surge horn. The motion of the auroral arc and the poleward boundary are closely tied to each other.

15 15 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

16 16 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

17 17 Shock aurora (Motoba et al., 2009, JGR) ASI at South Pole Sensitive to proton precipitation. Sudden increase in solar wind dynamic pressure results in intensification of dayside aurora. This is called shock aurora. Coordinated South Pole and IMAGE satellite observation found two step development of the shock aurora in the postnoon sector: Diffuse aurora first, followed by discrete aurora. Diffuse aurora may be associated with proton precipitation. Discrete aurora may be associated with electron precipitation. Response of dayside aurora to interplanetary shock Arrival of interplanetary shock Sensitive to electron precipitation. Diffuse aurora (due to proton precipitation) Discrete aurora (due to electron precipitation)

18 18 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

19 19 Major scientific results Quasi stationary auroral patches Ebihara et al. (2007, JGR), Tanaka et al. (JpGU, 2011) Evolution of discrete arc Figueiredo et al. (2005, AG) Shock aurora Motoba et al. (2009, JGR) Proton aurora associated with MIE Ebihara et al. (2010, JGR)

20 Proton aurora associated with MIE (Ebihara et al., 2010, JGR) 20 H D Z Hβ MIE Transient (5 15 min), large amplitude (>50 nt) magnetic field disturbances are observed at MLATs. This is called a magnetic impulse event (MIE). Electron precipitation is observed in association with MIEs (Mende et al., 1990, 2001; Weatherwax et al., 1999; Kataoka et al., 2001). We found intensification of auroral hydrogen emission (Hβ) associated with MIEs nm nm

21 Proton aurora associated with MIE (Ebihara et al., 2010, JGR) 21 /25 11:59:21 UT 12:00:12 UT 12:01:04 UT 11:58:55 UT 11:59:46 UT 12:00:37 UT 12:01:28 UT Hb nm 11:58:30 UT Poleward ~0830 MLT A patch of proton aurora appears associated with MIE. There is no significant intensification of brightness at nm, implying that the patch most likely results from proton precipitation. The appearance of the proton auroral patch may support the idea that MIE is caused by a localized compression of the dayside magnetosphere. When the magnetosphere is compressed, the perpendicular component of the protons are adiabatically accelerated, resulting in growth of EMIC waves that scatter the protons.

22 22 Selected papers related to all sky imager at South Pole Station Suzuki, S., M. Tsutsumi, S. E. Palo, Y. Ebihara, M. Taguchi, and M. Ejiri, J. Geophys. Res., 116, D19109, doi: /2011jd015882, Liu, J. J., H. Q. Hu, D. S. Han, T. Araki, Z. J. Hu, Q. H. Zhang, H. G. Yang, N. Sato, A. S. Yukimatu, and Y. Ebihara, Decrease of auroral intensity associated with reversal of plasma convection in response to an interplanetary shock as observed over Zhongshan station in Antarctica, J. Geophys. Res., 116, A03210, doi: /2010ja016156, Ebihara, Y., R. Kataoka, A. T. Weatherwax, and M. Yamauchi, Dayside proton aurora associated with magnetic impulse events: South Pole observations, J. Geophys. Res., 115, A04301, doi: /2009ja014760, Motoba, T., A. Kadokura, Y. Ebihara, H. Frey, A. T. Weatherwax, and N. Sato, Simultaneous ground satellite optical observations of postnoon shock aurora in the Southern Hemisphere, J. Geophys. Res., 114, A07209, doi: /2008ja014007, Ebihara, Y., Y. M. Tanaka, S. Takasaki, A. T. Weatherwax, and M. Taguchi, Quasi stationary auroral patches observed at the South Pole Station, Journal of Geophysical Research, 112, A01201, doi: /2006ja012087, Maynard, N. C., W. J. Burke, Y. Ebihara, D. M. Ober, G. R. Wilson, K. D. Siebert, J. D. Winningham, L. J. Lanzerotti, C. J. Farrugia, M. Ejiri, H. Reme, A. Balogh, and A. Fazakerley, Characteristics of merging at the magnetopause inferred from dayside nm all aky images: IMF drivers of poleward moving auroral forms, Annales Geophysicae, 24, , Figueiredo, S., G. T. Marklund, T. Karlsson, T. Johansson, Y. Ebihara, M. Ejiri, N. Ivchenko, P. A. Lindqvist, H. Nilsson, A. Fazakerley, Temporal and spatial evolution of discrete auroral arcs as seen by Cluster, Annales Geophysicae, Vol. 23, , Milan, S. E., N. Sato, M. Ejiri, Jø. Moen, Auroral forms and the field aligned current structure associated with field line resonances, Journal of Geophysical Research, 106(A11), , /2001JA900077, 2001.

23 Current status 23 Imager 1 Objective Lens Nikkor F1.4, f-6mm, 180 deg FOV Throughput A =0.91cm 2 str Filter (2003-) 427.8, 557.7, 630.0, 589.0, nm Imager 2 Imager 1 Camera Cooled CCD camera with spatial resolution of 512x512 pixels (corresponding to resolution of 0.7 km at 120 km altitude at zenith. Imager 2 Filter 481.3, 486.1, 671.0, and nm Camera Cooled EM-CCD camera with spatial resolution of 512x512 pixels (corresponding to resolution of 0.7 km at 120 km altitude at zenith. Imager 3 Filter Panchromatic Camera WATEC WAT-120N+ with spatial resolution of 570x480 pixels. 3 imagers (2 monochromatic and 1 panchromatic) are ready for observation. The data is available through the web: aurora.org/ Extension of this project was approved by NIPR on February 14.

24 24 Future perspective conjugate points Simultaneous auroral observation at a pair of conjugate points South Pole and Iqaluit in Canada in collaboration with Prof. Jayachandran. Such observations are possible in May and August for 2 weeks in total a year. One of the scientific targets is to investigate auroral structures near open closed boundary on nightside. Diurnal variation of conjugate point South Pole

25 25 Summary A large amount of valuable data has been obtained by ASIs at South Pole Station. ASI 1 has captured ~3M images. Scientific advances have been made. Data is open to public through the web. Data request and collaboration are welcome.