V1 and V2 Measurements of Galactic and Anomalous Cosmic Rays in the Outer Heliosphere and the Heliosheath during Solar Cycle #23   W.R. Webber (The CRS collaboration, E.C. Stone, F.B. McDonald, A.C. Cummings, B. Heikkila and N. Lal)   Paper given at the South African Workshop March 24, 2010

V1 at 112 AU, 35 N (2010.0) V2 at 91 AU, 29 S (2010.0) HTS – 85-95 AU, HP 120-125 AU

150-380 MeV He RI= 9.8%/yr Ratio = 1.60 x

RI= 23.5%/yr R=1.48x

130-240 MeV H RI= 18.5%/yr R=2.28x

RI= 100%/yr

6-14 MeV Galactic Electrons

The magnitude of the 11-year cycle, only ~35% at V2 and ~20% at V1. The magnitude of the 11-year cycle, a factor ~4 at the Earth

11 years of V1 observations

Helium energy spectrum at V1 between 2004. 5 and 2009 Helium energy spectrum at V1 between 2004.5 and 2009.5 during the sustained recovery period.

Helium spectra measured at three locations in the heliosphere at times of 11 year modulation minimum

H and He spectra measured at three locations in the heliosphere at times of 11 year modulation minimum

The integral (proton) intensity measured at V1 from 1997 to 2010

The V1 electron spectra between ~10 and 120 MeV during the time period after the HTS crossing. This electron spectrum is rapidly evolving toward two possible IS spectra as indicated. During this evolution the electron spectral slope remains constant and is very similar to the IS spectral slope calculated from galactic propagation models.

The lower energy H and He components contain a significant contribution from TSP at the lower energies and GCR at the highest energies. Note especially the similarity of intensities between V1 and V2 in 1998-99 and again in 2007-08 when these spacecraft were ~15-20 AU apart. Also note the amplitude on the 11 year modulation cycle which is clearly larger at V2 then V1, 15 AU further out.

The O component is almost purely anomalous

The normalized intensities of various energy O The normalized intensities of various energy O* nuclei from 2002 to the end of data.

The unfolding of the O* spectrum as V1 passes further beyond the HTS. At energies >15 MeV/nuc this spectrum has an index = -3.3. It becomes flatter at lower energies, between 4-7 MeV/nuc the index is ~2.1.

The 5 day running average rates for 4 individual CRS components: 1) TSP (1.7-2.9 MeV H), 2) ACR (27-42 MeV He), 3) Electrons (6-14 MeV) and 4)= GCR (>70 MeV). The most important features in the data are marked by vertical lines and shaded regions, along with the nominal distance in front of or behind the HTS at the top.

Thank you

Thank you for your attention V1 at 112 AU, 35 N (2010.0) V2 at 91 AU, 29 S (2010.0) HTS – 85-95 AU, HP 120-125 AU Thank you for your attention

Running commentary on V1 intensities beyond the HTS (5 Figures) Possible IS spectral intensities shown as IS-1 (W & L) and IS-2 (W & H) latest. Data beyond HTS in red. Figure ①: 150-380 MeV He – Rate of increase over last 2 years  RI RI= 9.8%/yr R=Ratio =1.60x Figure ②: 56-125 MeV C + O RI= 23.5%/yr R=1.48x (energy below peak in IS differential spectrum) Figure ③: 130-240 MeV H RI= 18.5%/yr R=2.28x (contains ~10-20% H* background) Figure ④: 6-14 MeV e RI= 100%/yr The most reliable indicators above (Figures 1 and 4) would suggest that the IS-2 spectrum will be reached at about 2012.0 when V1 will be at ~120 AU Figure ⑤: V1 & V2 6-14 MeV e Dramatic differences beyond the HTS! Difference at 2010.0, = 23.0!

Running commentary on SS#23 variations at the Earth, V2 and V1 (3 Figures) Here the distance of V1 is shown across the top in each figure and ranges from ~70 AU to 110AU. V1 crossed the HTS at the end of 2004. V2 is ~20 AU inside of V1 and crossed the HTS at 2007.67. Figure ⑥: This figure shows the intensity variations of 155-245 MeV He at the three locations, Earth, V2 and V1. The difference in intensities is a measure of the average IP radial gradient.   Note especially: (1) The magnitude of the 11-year cycle, a factor ~4 at the Earth, only ~35% at V2 and ~20% at V1. (2) The sustained recovery at all 3 locations starting at the end of 2004. (3) The very similar intensities at V1 and V2 during 1998-99 and again in 2007-08. Figure ⑦: This figures shows the intensity-time variations of different energy particles during SS#23 at the V1 spacecraft. Note especially: (1) The large magnitude (a factor ~2) of the 11-year cycle intensity changes at the two lowest rigidities 56- 125 MeV C+O and 155-195 H. (2) The reduced magnitude of these changes at higher rigidities, ~25% for 155-195 MeV He and only ~10% for 245-380 MeV He. (3) The much more rapid intensity recovery for protons than for C+O nuclei at about the same rigidity. Figure ⑧: This figure shows the evolution of the He energy spectrum at V1 between 2004.5 and 2009.5 during the sustained recovery period. Note especially: (1) The spectral unfolding which amounts to a factor ~1.5 increase at the highest energies (~500 MeV/nuc) to a factor ~2.5 increase near the spectral peak at ~150-175 MeV/nuc. (2) The spectral intensities which are decreasing at lower energies, consistent with the idea of a considerable residual solar modulation remaining beyond ~110 AU.

Running commentary on H and He spectra throughout the Heliosphere (2 Figures) These two figures show H and He spectra measured at 3 locations in the heliosphere at times of 11 year modulation minimum at: 1) the Earth in 1997 2) ~70 AU in 1998 3) ~110 AU in 2009 Calculations are shown at ~90 AU (approximate location of HTS) and at the Earth for a simple F.F. model assuming a W&H 2007, IS spectrum at 120 AU. These calculations are adjusted to fit the data at the Earth. A W&L 2001, IS spectrum is also shown in each Figure.   Figure ⑨: This figure shows the He spectra at the 3 locations along with calculations for a F.F. model with =120 MV (HTS) and 300 MV (Earth). Figure ⑩: This figure shows the H spectra at the 3 locations along with corresponding calculations for =120 and 300 MV. Note that the value of 300 MV required to reproduce the H (and He) spectrum at the Earth (from the IS W&H spectra) is much less than the commonly assumed values between 400-500 at SS min. These spectra have important implications for historical 10Be studies. They basically imply that the high 10Be concentrations measured at the Maunder minimum cannot be produced solely by production changes from cosmic rays as has been argued in the past but other effects may be equally important. Therefore the concentration cannot be directly used for an estimate of solar modulation at that time.

Running commentary on V2 CRS intensities before and after the HTS figure Figure ⑱: This figure shows the 5 day running average rates for 4 individual CRS components: 1)= TSP (1.7-2.9 MeV H), 2)=ACR (27-42 MeV He), 3)= Electrons (6-14 MeV) and 4)= GCR (>70 MeV). The most important features in the data are marked by vertical lines and shaded regions, along with the nominal distance in front of or behind the HTS at the top. In the foreshock region the two vertical green lines at ~0.75 and ~0.5 AU in front of the HTS indicate sharp decreases in most CRS components, particularly for 1.9-2.7 MeV H. We believe these decreases are caused by structures related to the HTS itself and not to propagating IP disturbances. These decreases are time coincident with sudden B field increases, identified as MIR’s by Burlaga, et al., and also to sudden decreases in the solar wind speed (opposite to that expected for an IP shock, for example) by Richardson, et al. Similar sudden decreases in these cosmic ray components are also seen in the CRS data just prior to the V1 crossing of the HTS 2.7 years earlier at about the same nominal distances in front of the HTS. After the HTS crossing at 2007.66, all CRS intensities continue to increase as they did at V1 until about 2007.8-2007.9 when a large decrease begins, as shown by the shaded region. In the middle of this general decrease there is a large transient decrease in the TSP at 2007.96 coincident with a sudden increase in 6-14 MeV electrons. We believe that these events, occurring when V2 was nominally 0.9 AU beyond the shock, are possibly due to the arrival at V2 of a large IP disturbance generated by the December 2006 events at the Sun (see Intriligator, et al., 2010). The sudden decrease/increase at 2007.96 was accompanied by a large increase in solar wind pressure. At its peak this pressure was as large as the solar wind pressure earlier in 2007 when V2 was ~2.0 AU in front of the shock. Later in 2008, between 2008.3 and 2008.45 another large decrease was observed in all 4 CRS components. This decrease was gradual and was accompanied by a general increase in solar wind pressure. V2 was a nominal 2.0 AU beyond the HTS at this time.

Running commentary on the anomalous components beyond the HTS (4 figures) The lower energy H and He components contain a significant contribution from TSP at the lower energies and GCR at the highest energies. The O component is almost purely anomalous so we will concentrate on it. Figure ⑭: Having said that we first show the time variations of 27-69 MeV He at V1 and V2 during the last 11 year cycle. Note especially the similarity of intensities between V1 and V2 in 1998-99 and again in 2007-08 when these spacecraft were ~15-20 AU apart. Also note the amplitude on the 11 year modulation cycle which is clearly larger at V2 then V1, 15 AU further out. Figure ⑮: This figure shows the recent 11 year solar modulation cycle variations at V1 and V2 for 7-17 MeV O* (the same total energy interval as for He in Figure 14). The temporal variations of the two components, He and O* are very similar, allowing for a significant GCR background in the He data that is most important at lower intensity levels. Figure ⑯: This figure shows the normalized intensities of various energy O* nuclei from 2002 to the end of data. Especially interesting is the energy dependence of the intensity time profiles beyond the HTS. The intensity peaks do not occur at the same time or distance, implying that the most effective acceleration occurs at different distances beyond the HTS for different energies. Figure ⑰: This figure shows the unfolding of the O* spectrum as V1 passes further beyond the HTS which was crossed at ~2005.0. At energies >15 MeV/nuc this spectrum has an index = -3.3. It becomes flatter at lower energies, between 4-7 MeV/nuc the index is ~2.1.

Running commentary on V1 intensities of nuclei and electrons beyond 100 AU and the approach to an IS intensity (3 Figures) These figures show both nuclei and electrons and two possible IS intensities of these components. Figure ⑪: This figure shows the integral (proton) intensity measured at V1 from 1997 to 2010 with reference to the integral intensities calculated for the two reference LIS spectra. The V1 intensity is within ~10% of the lower IS spectrum at 2010.0. Figure ⑫: This figure shows the 5d R average electron intensity at V1 (and V2) after 2004 when V1 crossed the HTS. Note particularly the uniform rate of increase at V1 after about 2008.5 when V1 was beyond ~105 AU. Modulation from outward moving IP shocks was very weak beyond this location At V2, after the HTS crossing at 2007.66, the intensity time profile is completely different and shows much structure. Figure ⑬: This figure shows the V1 electron spectra between ~10 and 120 MeV during the time period after the HTS crossing. This electron spectrum is rapidly evolving toward two possible IS spectra as indicated. During this evolution the electron spectral slope remains constant and is very similar to the IS spectral slope calculated from galactic propagation models.

Starting about 2008.59 several periodic decreases were observed in the 1.9-2.7 MeV TSP rate. These decreases have a period ~30-35 days. Periodic increases in the 6-14 MeV electron component occur during the same time period but are offset by ~ ½ a cycle. We believe that these periodic intensity changes may be due to the proximity of the heliospheric current sheet tilt. V2 at that time was at ~29 S. During this overall time period, the intensity of all components was slowly increasing. At about 2009.15, when V2 was a nominal 4.7 AU beyond the HTS, a long gradual intensity decrease lasting for ~0.25 year began for all 4 CRS components. The decrease was a factor of two for 1.9-2.7 MeV H (TSP) and for 6-14 MeV electrons, and 30% for 27-42 MeV He (ACR) and 5-10% for >70 MeV GCR. From 2009.5 to 2010.0 and beyond the intensity of all 4 CRS components remained at this lower level. The intensities during this time period were less than they were just before V2 crossed the HTS over two years earlier.