Long Term Measurements of Solar Wind Fe Charge States:

Charge State Distributions

Mark Popecki, A. Galvin, L. M. Kistler,H. Kucharek, E. Moebius, K. Simunac, P. Bochsler,

L. M. Blush, B. Klecker

Solar Wind Fe Charge State Expectations

• Four types (Schwenn, 2006)

– Fast solar wind (coronal holes)

– Slow solar wind (near helmet streamers

– Slow solar wind (active regions)

– ICME solar wind

• <QFe> slow > <QFe>fast

• ICME QFe ~16+• Small variations in mean

charge state compared to SEPs

slow

fast

Von Steiger et al., (2000)

STEREO A Fe Charge States vs. Solar Wind SpeedLatter Half of 2008

Q Fe

STEREO A solar wind speed/100 (km/s)•Limited period of time

•Solar wind speed is inversely related to Q Fe

Iron charge states and solar wind speeds : 2007 (DOY 022) -2009 (DOY 230), STEREO A

• The top trace is the iron charge state, averaged over 2 hour periods.

o The average charge states typically ranged between 8+ and 11+.

o A prominent exception occurred during the 2007/143 May 23 ICMEs. The average charge state was ~13+ to 14+.

• The bottom trace is the 2 hour averaged solar wind speed from STEREO A.

o An upward trend occurred in the beginning of 2008, maximizing at DOY 2007 400 (early February, 2008).

o A long decline below the 2007 levels followed, until August of 2009.

o Variations in the solar wind speed have decreased compared to early 2007.

2007/143 May 22-24 ICME

S/W

spe

ed /

100

and

< Q

Fe

>

2007 20082009

Mean Iron Charge State and Solar Wind Speed: 2007 (DOY 022) -2009 (DOY 230), STEREO A

• The smoothed trendline in the iron charge states is shown in blue (left axis) with the smoothed trendline for the solar wind speed.

• The iron charge state tends to move in the opposite direction to the solar wind speed in a large scale sense.

• The charge state in 2008/2009 has not completely recovered to the early 2007 levels, even though the average solar wind speed has gone lower than it was in 2007.

8.6

8.7

8.8

8.9

9.0

9.1

9.2

9.3

9.4

9.5

0 200 400 600 800 1000

DOY 2007

< Q Fe > (smoothed: 400 2hr points)

300

350

400

450

500

550

Solar Wind Speed (smoothed: 400 2 hr pts) STA Q Fe

STA S/W Speed

QFe

S/W speed

2007 20082009

Mean Iron Charge State and Solar Wind Speed: 2007 (DOY 022) -2009 (DOY 230), STEREO A

• The smoothed trendline in the iron charge states is shown in blue (left axis) with the smoothed trendline for the solar wind speed.

• The iron charge state tends to move in the opposite direction to the solar wind speed in a large scale sense.

• The charge state has not completely recovered to the early 2007 levels, even though the average solar wind speed has gone lower than it was in 2007.

8.6

8.7

8.8

8.9

9.0

9.1

9.2

9.3

9.4

9.5

0 200 400 600 800 1000

DOY 2007

< Q Fe > (smoothed: 400 2hr points)

300

350

400

450

500

550

Solar Wind Speed (smoothed: 400 2 hr pts) STA Q Fe

STA S/W Speed

QFe

S/W speed

2007 20082009

Iron Charge State and Solar Wind Speed: A change in the Fe charge state distribution in the 410-435 km/s

S/W speed range

• Fe charge histograms were calculated for two periods in 2007 and 2008 for which solar wind speeds were 410 - 435 km/s.

• The Fe charge state histogram for 2008 is narrower and has less high charge content than in the 2007 period.

0

10000

20000

30000

40000

50000

60000

70000

80000

4 5 6 7 8 9 10 11 12 13 14 15 16 17

QFe

2007 Qty

0

2000

4000

6000

8000

10000

12000

2008 Qty

2007 period 2008 period

410 - 435 km/s

8.6

8.7

8.8

8.9

9.0

9.1

9.2

9.3

9.4

9.5

0 200 400 600 800 1000

DOY 2007

< Q Fe > (smoothed: 400 2hr points)

300

350

400

450

500

550

Solar Wind Speed (smoothed: 400 2 hr pts) STA Q Fe

STA S/W Speed

QFe

S/W speed

2007

2008

2009

SummaryChanges in Fe charge state distributions with solar

wind speed

• In the 2007-2009 period, the solar wind speed trended up, then down again.

• The mean Fe charge state varied inversely, consistent with von Steiger et al. (2000).

• However, in the second low speed period, the mean Fe charge state was lower than the first.

• For the speed range 410 - 435 km/s, the Fe charge state distribution in the second period was narrower than in the first, due to a deficit in higher charge states.

• Is the slow solar wind in the second period from a different source than the first?

Solar Wind Speeds: Recent Solar Min and Max

• STEREO A: 2007/045-2009/230

• ACE: 1998-2005.5

• Speeds in the 2007-2009 period (solar min) are typically lower than the 1998-2005 period (solar max)

0

100

200

300

400

500

600

700

0 200 400 600 800 1000 1200

STA 2007-2009 S/W Speeds (km/s)

Counts (STA)

0

500

1000

1500

2000

2500

3000

3500

Counts (ACE)

STA 2007-2009

ACE S/W Speeds 1998-2005.5

0

1000

2000

3000

4000

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6000

7000

4 5 6 7 8 9 10 11 12 13 14 15 16 17

QFe

Qty

0

500

1000

1500

2000

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3000

3500

Qty

2007 149.1-149.9 2008 251.1-252.1

Contiguous 2hr samples

• 2007 vs 2008 for 410-435 km/s

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0 5 10 15 20

QFe

2007 Qty

0

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2008 Qty

2007 period 2008 period

410 - 435 km/s

normSTA_2007_133-222_2008_190-258_ST tail data.txtqoftdata.xls

0

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20000

25000

0 5 10 15 20

QFe

2007 Qty

0

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2008 Qty

2007 period 2008 period

425 - 435 km/s

•NSO/GONG synoptic coronal hole plots for selected Carrington rotations

– Red/green areas are coronal holes: red negative polarity, green positive polarity

– Neutral line is in black

• Isolated coronal holes disappear with time

• Polar coronal hole extensions shrink

• Neutral line flattens (less tilted current sheet)

• Reduced exposure to coronal hole solar wind?

Galvin et al., 2009

• One hour averages of solar wind speed and iron charge state from STEREO A

• Smoothed lines - 655 hour averages (~Carrington rotation)

STEREO A Fe Charge States vs. Solar Wind Speed

0

2

4

6

8

10

12

14

25 125 225 325 425 525 625 725

DOY 2007

<QFe>

100

300

500

700

900

1100

1300

Solar Wind Speed (km/s)

• Average Fe charge state generally shows an anticorrelation with solar wind speed (sources: fast or slow s/w, coronal holes or active region).

• Typical values of charge state are between 9+ and 10+.

• Only one period of high charge states exists: May 22-24, 2007 (ICME).

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

< Q

Fe

>

Solar Wind Speed (STEREO A, km/s)

0 200 400 600 800

slow

fast

Von Steiger et al., (2000)

Solar Wind Speed vs. Iron Charge State STEREO A 2007-2009

• The mean iron charge states are plotted against corresponding solar wind speeds for the 2007-2009 period.

• Variations in charge state are generally related to solar wind speed, but with a broad spread of approximately 1-2 charge units.

• The mean Q Fe goes up at low speed, as von Steiger et al. (2000) reported.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

< Q

Fe

>

Solar Wind Speed (STEREO A, km/s)

0 200 400 600 800

slow

fast

Von Steiger et al., (2000)