Heliospheric Current Sheet Tilt Research Articles

Constraining the charge-, time-, and rigidity-dependence of cosmic-ray solar modulation with AMS-02 observations during Solar Cycle 24

Our basic theoretical understanding of the sources of cosmic rays and their propagation through the interstellar medium is hindered by the Sun, that through the solar wind affects the observed cosmic-ray spectra. This effect is known as solar modulation. Recently released cosmic-ray observations from the Alpha Magnetic Spectrometer (AMS-02) and publicly available measurements of the solar wind properties from the Advanced Composition Explorer and the Wilcox observatory allow us to test the analytical modeling of the time-, charge- and rigidity-dependence of solar modulation. We rely on associating measurements on the local heliospheric magnetic field and the heliospheric current sheet's tilt angle, to model the time-dependence and amplitude of cosmic-ray solar modulation. We find evidence for the solar modulation's charge- and rigidity-dependence during the era of solar cycle 24. Our analytic prescription to model solar modulation can explain well the large-scale time-evolution of positively charged cosmic-ray fluxes in the range of rigidities from 1 to 10 GV. We also find that cosmic-ray electron fluxes measured during the first years of cycle 24 are less trivial to explain, due to the complex and rapidly evolving structure of the Heliosphere's magnetic field that they experienced as they propagated inwards.

Solar Modulation of Galactic Cosmic-Ray Protons Based on a Modified Force-field Approach

Abstract In this work, a modified force-field approach is established to investigate the long-term solar modulation of galactic cosmic-ray (GCR) protons. In this approach, the solar modulation potential ϕ is assumed to be energy dependent. As ϕ also depends on the local interstellar spectrum (LIS), a new proton LIS model is first presented based on data from Voyager 1 and 2, PAMELA, and AMS-02. Then, a double power-law expression is proposed to model ϕ as a function of proton energy. By fitting to the selected GCR measurements, the solar cycle variation characteristics of parameters in the expression of ϕ are obtained, and these parameters are reconstructed using the sunspot number, the heliospheric current sheet tilt angle, and the polarity of heliospheric magnetic field. Finally, a new analytical predictive model for GCR protons is established. It is shown that the 11 and 22 yr cyclic variations of GCRs are reproduced, and the computed proton intensities are in good agreement with GCR measurements at various energies since 1954.

The Effects of Solar Wind Structure on Nanodust Dynamics in the Inner Heliosphere

AbstractSeveral interplanetary spacecraft have inferred the presence of nanometer‐sized dust grains in the inner heliosphere accelerated to near‐solar wind velocities based on observations by radio wave antennas. These “nanodust” grains exhibit unique behavior in interplanetary space as they are strongly affected by both the solar gravitational force and the electromagnetic Lorentz force from the convecting interplanetary magnetic field. Here, we study the dynamics of nanodust grains in the inner heliosphere via a combination of background electromagnetic fields from the coupled Wang‐Sheeley‐Arge/Enlil heliospheric model and a nanodust grain charging and dynamics model. The model results predict strong time variability in the nanodust velocity and flux distributions at 1 au within a single Carrington rotation (CR) driven by a combination of nanodust grain size, heliospheric current sheet tilt, and varying heliospheric plasma parameters. In contrast, the general character of nanodust dynamics does not drastically change from one CR to the next. Despite including observationally driven heliospheric plasma conditions, the modeled nanodust impact rates do not agree with in situ observations by the STEREO A and B WAVES instruments, especially with regard to CR‐to‐CR variability. We interpret this data‐model disagreement as evidence that additional time variability must be present in the production rate of nanodust grains in the inner heliosphere. We discuss possibilities for this time variability, including non‐steady‐state collisional cascades, variability in nanodust trapping regions, and the impulsive disruption of inner solar system comets and/or asteroids.

Asymmetric Latitudinal Gradients of Galactic Cosmic Rays at Low and High Cutoff Rigidities in Two Negative Solar Magnetic Cycles: Solar Cycles 21/22 and 23/24

The south–north asymmetry of the Galactic cosmic-ray (GCR) density [ $n$ ] denoted as $\delta n_{\text{S-N}}/n$ with respect to the heliospheric current sheet (HCS), observed by neutron monitors at low (≈ 1 GV) and high (≈ 13 and ≈ 17 GV) cutoff rigidities [ $P_{\text{c}}$ ], is investigated in two negative solar magnetic polarities when the dominant polar field is toward the northern hemisphere of the Sun. Using a new simple correction method for secular changes due to solar activity for the $\delta n_{\text{S-N}}/n$ reveals that it is inversely rigidity dependent. Annual values of the corrected $\delta n_{\text{S-N}}/n$ are close to zero in both solar magnetic cycles and exhibit substantial deviations due to their temporal 27-day variations. After corrections for Earth’s excursions in helio-latitude for the north–south (NS) differences of HCS tilt angle [ $\alpha$ ] as $\Delta\alpha_{ \text{N-S}}^{\text{E}}$ , the number of 27.3-day Carrington rotations that possess correspondences between the corrected $\delta n _{\text{S-N}}/n$ and $\Delta\alpha_{\text{N-S}}^{\text{E}}$ in both solar cycles (SCs) is significantly increased. Correlations of the two parameters are considerably increased in both SCs, particularly for SC 21/22. The asymmetric or unidirectional latitudinal gradients [ $G _{\perp}$ ] derived from the consistencies between corrected $\delta n_{\text{S-N}}/n$ and $\Delta\alpha_{\text{N-S}}^{ \text{E}}$ for the low and high $P_{\text{c}}$ in the SC 21/22 are 1.38% AU−1 and 0.69% AU−1, respectively, which are a few times larger than of SC 23/24. This suggests that asymmetric cosmic-ray modulation by the asymmetric HCS is more pronounced in SC 21/22 than in SC 23/24. Although the corrections also provide results that are fairly consistent with the drift model for the symmetric or bidirectional latitudinal gradient [ $G_{z}$ ], the effects of the SN asymmetric modulation of the GCR density are important as well. It is found that $G_{\perp}$ , $G_{z}$ , and SN asymmetric GCR modulation by NS asymmetric solar-wind speed are also inversely dependent on rigidity. The interplay between SN asymmetric modulation of the GCR density by the asymmetries in HCS and solar-wind speed, together with the effects of diffusion, are discussed for both of the negative solar magnetic cycles.

Modeling Solar Energetic Particle Transport near a Wavy Heliospheric Current Sheet

Abstract Understanding the transport of solar energetic particles (SEPs) from acceleration sites at the Sun into interplanetary space and to the Earth is an important question for forecasting space weather. The interplanetary magnetic field (IMF), with two distinct polarities and a complex structure, governs energetic particle transport and drifts. We analyze for the first time the effect of a wavy heliospheric current sheet (HCS) on the propagation of SEPs. We inject protons close to the Sun and propagate them by integrating fully 3D trajectories within the inner heliosphere in the presence of weak scattering. We model the HCS position using fits based on neutral lines of magnetic field source surface maps (SSMs). We map 1 au proton crossings, which show efficient transport in longitude via HCS, depending on the location of the injection region with respect to the HCS. For HCS tilt angles around 30°–40°, we find significant qualitative differences between A+ and A− configurations of the IMF, with stronger fluences along the HCS in the former case but with a distribution of particles across a wider range of longitudes and latitudes in the latter. We show how a wavy current sheet leads to longitudinally periodic enhancements in particle fluence. We show that for an A+ IMF configuration, a wavy HCS allows for more proton deceleration than a flat HCS. We find that A− IMF configurations result in larger average fluences than A+ IMF configurations, due to a radial drift component at the current sheet.

Modulation of Galactic Cosmic Rays in the Inner Heliosphere, Comparing with PAMELA Measurements

Abstract We develop a numerical model to study the time-dependent modulation of galactic cosmic rays in the inner heliosphere. In the model, a time-delayed modified Parker heliospheric magnetic field (HMF) and a new diffusion coefficient model, NLGCE-F, from Qin & Zhang, are adopted. In addition, the latitudinal dependence of magnetic turbulence magnitude is assumed to be from the observations of Ulysses, and the radial dependence is assumed to be , where we choose an expression of S as a function of the heliospheric current sheet tilt angle. We show that the analytical expression used to describe the spatial variation of HMF turbulence magnitude agrees well with the Ulysses, Voyager 1, and Voyager 2 observations. By numerically calculating the modulation code, we get the proton energy spectra as a function of time during the recent solar minimum, it is shown that the modulation results are consistent with the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics measurements.

Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution.

Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25.

The Solar Polar Field in the Cosmic-Ray Intensity Modulation

In this work the modulation of galactic cosmic-ray intensity based on solar and heliospheric indices for the solar cycle 23 (1996-2008), is studied. In previous works a number of different indices such as the sunspot number, the CME-index, the interplanetary magnetic field and the heliospheric current sheet tilt were selected to be the most appropriate ones in order to describe the cosmic ray intensity of 10 GV observed by the network of neutron monitors. The new approach is an extension of this study to the influence of the solar magnetic field parameters, such as the mean magnetic field and the polar magnetic field, on the cosmic ray (CR) modulations. Using the wavelet analysis method a major periodicity of about 20-21 years was confirmed in the solar magnetic field data, indicating the existence of the solar magnetic cycle in CR variations. The best empirical relation of the cosmic ray modulation taking into account the sunspot number, the CME-index, the mean solar magnetic field and the solar polar field was improved significantly: a relative root mean square deviation (RMSD) between the observed and the calculated cosmic ray intensity values is found to be 8.7% instead to the previous one of about 10%.

The heliospheric Hale cycle over the last 300 years and its implications for a “lost” late 18th century solar cycle

A Hale cycle, one complete magnetic cycle of the Sun, spans two complete Schwabe cycles (also referred to as sunspot and, more generally, solar cycles). The approximately 22-year Hale cycle is seen in magnetic polarities of both sunspots and polar fields, as well as in the intensity of galactic cosmic rays reaching Earth, with odd- and even-numbered solar cycles displaying qualitatively different waveforms. Correct numbering of solar cycles also underpins empirical cycle-to-cycle relations which are used as first-order tests of stellar dynamo models. There has been much debate about whether the unusually long solar cycle 4 (SC4), spanning 1784–1799, was actually two shorter solar cycles combined as a result of poor data coverage in the original Wolf sunspot number record. Indeed, the group sunspot number does show a small increase around 1794–1799 and there is evidence of an increase in the mean latitude of sunspots at this time, suggesting the existence of a cycle “4b”. In this study, we use cosmogenic radionuclide data and associated reconstructions of the heliospheric magnetic field (HMF) to show that the Hale cycle has persisted over the last 300 years and that data prior to 1800 are more consistent with cycle 4 being a single long cycle (the “no SC4b” scenario). We also investigate the effect of cycle 4b on the HMF using an open solar flux (OSF) continuity model, in which the OSF source term is related to sunspot number and the OSF loss term is determined by the heliospheric current sheet tilt, assumed to be a simple function of solar cycle phase. The results are surprising; Without SC4b, the HMF shows two distinct peaks in the 1784–1799 interval, while the addition of SC4b removes the secondary peak, as the OSF loss term acts in opposition to the later rise in sunspot number. The timing and magnitude of the main SC4 HMF peak is also significantly changed by the addition of SC4b. These results are compared with the cosmogenic isotope reconstructions of HMF and historical aurora records. These data marginally favour the existence of SC4b (the “SC4b” scenario), though the result is less certain than that based on the persistence of the Hale cycle. Thus while the current uncertainties in the observations preclude any definitive conclusions, the data favour the “no SC4b” scenario. Future improvements to cosmogenic isotope reconstructions of the HMF, through either improved modelling or additional ice cores from well-separated geographic locations, may enable questions of the existence of SC4b and the phase of Hale cycle prior to the Maunder minimum to be settled conclusively.

Corotating interaction regions and the 27 day variation of galactic cosmic rays intensity at 1 AU during the cycle 23/24 solar minimum

AbstractWe investigate the formation and evolution of corotating interaction regions (CIRs) in the solar wind and their effects on galactic cosmic rays (GCR) during the recent solar cycle 23/24 solar minimum. The output from a three‐dimensional MHD model serves as background for kinetic time‐dependent simulations of GCR transport based on the Parker equation. The results show that the CIR forward/reverse shock pairs or compression/rarefaction regions play important roles in the transport of GCR particles and directly control the observed 27 day periodic intensity variations. We find that stream interfaces (SIs) in CIRs and the heliospheric current sheet (HCS) are both closely associated with the GCR depression onset, in agreement with the observations at 1 AU. The HCS is more important when its tilt angle becomes small during the declining phase of the solar minimum, while the passages of SIs control the onset of GCR depressions for larger HCS tilt angles. The mechanism of GCR intensity variation near 1 AU can be explained through an interplay between the effects of particle drift and diffusion. The simulated plasma background and GCR intensity are compared with the observations from spacecraft and a neutron monitor on the ground, to find good qualitative agreement. Evidently, CIRs had a substantial modulational effect on GCR during the recent solar minimum.

Galactic Cosmic Ray Modulation and the Last Solar Minimum

In this work the galactic cosmic ray modulation in relation to solar activity indices and heliospheric parameters during the years 1996 – 2010 covering solar cycle 23 and the solar minimum between cycles 23 and 24 is studied. A new perspective of this contribution is that cosmic ray data with a rigidity of 10 GV at the top of the atmosphere obtained from many ground-based neutron monitors were used. The proposed empirical relation gave much better results than those in previous works concerning the hysteresis effect. The proposed models obtained from a combination of solar activity indices and heliospheric parameters give a standard deviation < 10 % for all the cases. The correlation coefficient between the cosmic ray variations of 10 GV and the sunspot number reached a value of r=−0.89 with a time lag of 13.6±0.4 months. The best reproduction of the cosmic ray intensity is obtained by taking into account solar and interplanetary indices such as sunspot number, interplanetary magnetic field, CME index, and heliospheric current sheet tilt. The standard deviation between the observed and calculated values is about 7.15 % for all of solar cycle 23; it also works very well during the different phases of the cycle. Moreover, the use of the cosmic ray intensity of 10 GV during the long minimum period between cycles 23 and 24 is of special interest and is discussed in terms of cosmic ray intensity modulation.

Cyclic loss of open solar flux since 1868: The link to heliospheric current sheet tilt and implications for the Maunder Minimum

Open solar flux (OSF) variations can be described by the imbalance between source and loss terms. We use spacecraft and geomagnetic observations of OSF from 1868 to present and assume the OSF source, S, varies with the observed sunspot number, R. Computing the required fractional OSF loss, χ, reveals a clear solar cycle variation, in approximate phase with R. While peak R varies significantly from cycle to cycle, χ is surprisingly constant in both amplitude and waveform. Comparisons of χ with measures of heliospheric current sheet (HCS) orientation reveal a strong correlation. The cyclic nature of χ is exploited to reconstruct OSF back to the start of sunspot records in 1610. This agrees well with the available spacecraft, geomagnetic, and cosmogenic isotope observations. Assuming S is proportional to R yields near‐zero OSF throughout the Maunder Minimum. However, χ becomes negative during periods of low R, particularly the most recent solar minimum, meaning OSF production is underestimated. This is related to continued coronal mass ejection (CME) activity, and therefore OSF production, throughout solar minimum, despite R falling to zero. Correcting S for this produces a better match to the recent solar minimum OSF observations. It also results in a cycling, nonzero OSF during the Maunder Minimum, in agreement with cosmogenic isotope observations. These results suggest that during the Maunder Minimum, HCS tilt cycled as over recent solar cycles, and the CME rate was roughly constant at the levels measured during the most recent two solar minima.

Long-Term Cosmic Ray Variability and the CME-Index

The cosmic ray modulation in relation to solar activity indices and heliospheric parameters during the period January 1996–October 2011, covering the solar cycle 23 and the ascending phase of solar cycle 24, is studied. The new perspective of this contribution is that the CME-index, obtained from only the CMEs with angular width greater than 30 degrees, gives much better results than in previous works. The proposed model for the calculation of the modulated cosmic ray intensity obtained from the combination of solar indices and heliospheric parameters gives a very satisfactory value of the standard deviation. The best reproduction of the cosmic ray intensity is obtained by taking into account solar and interplanetary indices such as sunspot number, interplanetary magnetic field, CME-index, and heliospheric current sheet tilt. The standard deviation between the observed and calculated values is about 6.63% for the solar cycle 23 and 4.13% for the ascending part of solar cycle 24.

Anomalous and Galactic Cosmic Rays at 1 AU During the Cycle 23/24 Solar Minimum

Anomalous cosmic ray (ACR) intensities at 1 AU at solar minimum generally track galactic cosmic ray (GCR) intensities such as those measured by neutron monitors, albeit with differences between solar polarity cycles. The unusual cycle 23/24 solar minimum was long-lasting with very low sunspot numbers and significantly reduced interplanetary magnetic field strength and solar wind dynamic pressure and turbulence, but also featured a heliospheric current sheet tilt that remained high for an extended period. Peak ACR intensities did not recover to the maximum values reached during the last two A>0 solar minima and just barely reached the last A<0 levels. However, GCR intensities in 2009 (neutron monitor rates and also at ∼200 MeV/nucleon) were the highest recorded during the last 50 years, indicating their intensities were not as heavily modulated during their transport from the outer heliosphere. This unexpected difference in the behavior of ACRs and GCRs remains unexplained, but suggests that either the ACR source intensity may have weakened since the last A<0 epoch, or perhaps that ACR intensities at 1 AU in the ecliptic may be more sensitive than GCRs to the higher tilt angle. This seems plausible if the ACR source intensity is greater at low latitudes during A<0 cycles, while the GCR distribution at the heliospheric boundary is more uniform in latitude. Shortly after an abrupt increase in the current sheet tilt angle in late 2009, both ACR and GCR intensities showed dramatic decreases, marking the end of solar minimum modulation conditions for this cycle.

Heliospheric current sheet and GCR modulation in 1976–2007

The correlation between the GCR intensity and the tilt of the heliospheric current sheet (HCS) during three solar cycles is considered. The correlation coefficients for the periods of decreasing and increasing intensity have been calculated, and the time lag of the GCR variations delay relative to changes in the HCS tilt has been determined. It has been shown that the correlation coefficients are independent of the heliospheric magnetic field (HMF) direction. The possible diffusive mechanism, by which the current sheet tilt is related to the GCR intensity, is briefly discussed.

Stochastic simulation of cosmic ray modulation including a wavy heliospheric current sheet

We present a quasi‐steady two‐dimensional (axisymmetric) model of the heliospheric transport of galactic cosmic rays. The model is based on stochastic simulation techniques and includes all the modulation mechanisms that cosmic rays experience in the heliosphere: convection, adiabatic cooling, diffusion, and drifts. A special emphasis is given to the cosmic ray transport in the vicinity of the heliospheric current sheet (HCS), and a new method to calculate the wavy current sheet drift is presented. We study cosmic ray modulation in different solar modulation conditions and levels of waviness of the current sheet. We discuss changes in the cosmic ray spectrum and the dominant streaming patterns of cosmic rays in the heliosphere for different solar polarities and HCS tilt angles.

Cyclic variations of the heliospheric tilt angle and cosmic ray modulation

Using data on cosmic ray modulation parameter since 1951, we have estimated the evolution of the heliospheric current sheet tilt angle for the period 1951–1975, i.e., 25 years before regular observations of the tilt angle. This estimate is based on our recent empirical model relating cosmic ray intensity with global heliospheric parameters. We propose a simple model to describe the cyclic evolution of the tilt angle with the solar cycle. This model agrees with available observational data. Using this model, we have estimated the cosmic ray intensity since 1710. This estimate is consistent with the results based on cosmogenic isotopes ( 14C and 10Be).

Reconstruction of the Heliospheric Current Sheet Tilts Using Sunspot Numbers

We have investigated the correlation between the relative sunspot number and tilt of the heliospheric current sheet (HCS) in solar cycles 21–23. Strong and highly significant positive correlation (r > 0.8, P < 0.001) was found for corresponding data in the time interval from May 1976 through December 2004. Cross-correlation analysis does not reveal any time shift between the data sets. Reconstructed values of the HCS tilt, for the time interval before 1976, are found using sunspot numbers. To take different amplitude of solar cycles into account they were then normalized to zero in the minima of the solar activity and to average in solar cycles 21–23 maximal calculated HCS tilt in the maxima. These normalized reconstructed HCS data are compared with the angular positions of the brightest coronal streamers observed during total solar eclipses in 1870–2002, and their agreement is better for the minima of the solar activity than for the maxima.

Intensities of galactic cosmic rays of ∼1.5 GV rigidity at Earth versus the heliospheric current sheet tilt

In this paper we have compared the cosmic ray intensity variations at ∼1.5 GV rigidity with the corresponding time variations of the heliospheric current sheet tilt (HCST). These studies extend earlier work comparing neutron monitor variations with the HCST. In addition to the results of this earlier work we have found that (1) the delay of the cosmic ray intensity changes relative to the HCST changes is much less in 11‐year cycles starting in a negative solar magnetic cycles. (2) During the specific periods of actual changeover of the solar magnetic field from positive to negative polarity, the cosmic ray intensity decrease is ∼50% of the total 11‐year cycle intensity decrease. During the changeover from negative to positive polarity, the entire cosmic ray 11‐year decrease has almost fully occurred before the polarity changeover. (3) In 11‐year modulation cycles starting in a negative polarity period, the regression coefficient between the cosmic ray intensity and tilt is ∼0.9% per degree of tilt during both the decreasing and increasing phases. In the 11‐year modulation cycles starting in a positive polarity cycle, the regression coefficient is much smaller, only ∼0.4% per degree during much of the cycle; then it becomes much steeper toward the end of the cycle. These features are discussed in terms of current models for cosmic ray modulation that include diffusion, convection, drifts, and the wavy current sheet.

Voyager and Pioneer spacecraft measurements of cosmic ray intensities in the outer heliosphere: Toward a new paradigm for understanding the global modulation process: 2. Maximum solar modulation (1990–1991)

In this paper we present interplanetary radial intensity profiles of five particle energies/species of cosmic rays measured by the IMP, Voyager 1, Voyager 2, and Pioneer 10 spacecraft at the time of maximum solar modulation in 1990–1991. These radial profiles are then compared with those measured in 1987 at a period of minimum modulation in order to examine the radial dependence of the 11‐year solar modulation effects. It is found that the radial intensity profiles observed in 1990–1991 can be described to first order by simple reduction factors of the radial profiles observed in 1987. These reduction factors range from ∼2.5 at the highest rigidities to ∼10 at the lowest rigidities measured here. These reduction factors describe the magnitude of the 11‐year modulation and imply that the intensities at the estimated location of the termination shock (TS), here taken to be at 88 AU, are reduced by a corresponding factor to those at the Earth at each energy. Therefore these TS intensities range from only 0.4 to 0.05 of the estimated IS intensities at the highest to lowest rigidities, respectively. This implies that most of the overall (11‐year and residual) modulation at this time and at these rigidities is occurring beyond the TS. Some of this 11‐year modulation (∼50% or less) occurs within this location. This part of the modulation is usually described in the present modulation models by invoking changing heliospheric current sheet tilt and changes in the drift and diffusion coefficients. However, overall, the 11‐year solar modulation, at least at the rigidities examined here, is most properly described as an outer heliospheric modulation phenomenon occurring mainly at or beyond the TS with a secondary (weaker) modulation occurring inside the TS. This is similar to the situation described by Webber and Lockwood [this issue], where the dominant modulation at times of minimum (residual) solar modulation also appears to occur in the outer heliosphere near to or beyond the TS. This large outer heliosphere modulation remains largely unexplained in present modulation theories. A new paradigm in solar modulation theory is required to more fully account for the large fraction of the 11‐year and/or residual solar modulation that is occurring in the outer heliosphere near to or beyond the TS.