Secular Acceleration Research Articles

Detection of secular acceleration pulses from magnetic observatory data

Geomagnetic secular variation (SV) models for the epochs before the space era are based on magnetic observatory data, which represent relatively rough and noisy time series due to magnetic storms, anthropogenic spikes and gaps. These models are often strongly regularized in time, so that fast variations in the SV are smoothed out. However, recent studies show that at least some of the geomagnetic jerks observed at the Earth’s surface emanate from increasing and decreasing phases of secular acceleration (SA) pulses at the core surface. The latter ones are direct manifestation of the dynamic processes taking place in the liquid core. They were first detected from satellite data, which are both of higher quality and more homogeneous in terms of geographical coverage than ground data. Herein we attempt to carry out similar studies based on observatory data available for a longer period. The proposed method of SV modeling and recognition of SA pulses relies on a new technique of processing time series based on fuzzy mathematics. Comparison with the SV modeling results derived from satellite data shows their high conformity with the proposed method. Stability and reliability of the SA pulse recognition are demonstrated by the examples of well-studied SA pulses in 2006, 2009 and 2012. Moreover, several new SA pulses around 1996, 1999, 2002 and 2014 are discovered as a result of the new approach application to multi-observatory data analysis. The latter provides a basis for applying the method to older historical data and investigate SA pulses and geomagnetic jerks further back in time.

After some 350 years – zero declination again in Paris

Abstract. The main part of the geomagnetic field – produced by a dynamo process in the Earth's outer core – changes its direction and strength in time, over timescales from months to centuries, even millennia. Its temporal variations, known as secular variation and secular acceleration, are crucial ingredients for understanding the physics of the deep Earth. Very long series of measurements therefore play an important role. Here, we provide an updated series of geomagnetic declination in Paris, shortly after a very special occasion: its value has reached zero after some 350 years of westerly values. Indeed, during October and November 2013, the declination at the Chambon la Forêt geomagnetic observatory changed from westerly to easterly values, the agonic line then passing through this place. We take this occasion to emphasize the importance of long series of continuous measurements.

A secular acceleration: Theological foundations of the sociological concept “social acceleration”

The term “shortening of time” is related to the Judeo-Christian tradition that announces the end of time as the moment when God, for the sake of the elect, shortens the duration of days and hours, because without this shortening no one would survive (This means that only a God's will could ended Time. The Christian perspective believes that the last days will be chaotic, and God will preclude History, ending time, to save a few men of goodwill.). While in this sense salvation is associated with divine intervention, the thesis of acceleration would reverse the above formula, making human beings responsible for the narrowing of time. But if the shortening of time in the Apocalypse is aimed at the salvation of the World: Where does acceleration, a secular idea of the shortening of time, aim? What is it that justifies the increase in the speed of completing tasks that previously took considerable time, which are today performed in just a few hours? How can we justify the frenzy to obtain what we want in the shortest time possible? In this paper we propose to address this and other questions, in order to show the relationship between a sociological understanding of acceleration with a theological-Christian view of time. In other words, the main claim exposes the transfer of teleology from a religious conception to a historical-worldly conception of time.

Recent geomagnetic secular variation from Swarm and ground observatories as estimated in the CHAOS-6 geomagnetic field model

We use more than 2 years of magnetic data from the Swarm mission, and monthly means from 160 ground observatories as available in March 2016, to update the CHAOS time-dependent geomagnetic field model. The new model, CHAOS-6, provides information on time variations of the core-generated part of the Earth’s magnetic field between 1999.0 and 2016.5. We present details of the secular variation (SV) and secular acceleration (SA) from CHAOS-6 at Earth’s surface and downward continued to the core surface. At Earth’s surface, we find evidence for positive acceleration of the field intensity in 2015 over a broad area around longitude 90°E that is also seen at ground observatories such as Novosibirsk. At the core surface, we are able to map the SV up to at least degree 16. The radial field SA at the core surface in 2015 is found to be largest at low latitudes under the India–South-East Asia region, under the region of northern South America, and at high northern latitudes under Alaska and Siberia. Surprisingly, there is also evidence for significant SA in the central Pacific region, for example near Hawaii where radial field SA is observed on either side of a jerk in 2014. On the other hand, little SV or SA has occurred over the past 17 years in the southern polar region. Inverting for a quasi-geostrophic core flow that accounts for this SV, we obtain a prominent planetary-scale, anti-cyclonic, gyre centred on the Atlantic hemisphere. We also find oscillations of non-axisymmetric, azimuthal, jets at low latitudes, for example close to 40°W, that may be responsible for localized SA oscillations. In addition to scalar data from Orsted, CHAMP, SAC-C and Swarm, and vector data from Orsted, CHAMP and Swarm, CHAOS-6 benefits from the inclusion of along-track differences of scalar and vector field data from both CHAMP and the three Swarm satellites, as well as east–west differences between the lower pair of Swarm satellites, Alpha and Charlie. Moreover, ground observatory SV estimates are fit to a Huber-weighted rms level of 3.1 nT/year for the eastward components and 3.8 and 3.7 nT/year for the vertical and southward components. We also present an update of the CHAOS high-degree lithospheric field, making use of along-track differences of CHAMP scalar and vector field data to produce a new static field model that agrees well with the MF7 field model out to degree 110.

The SOPHIE search for northern extrasolar planets

We report the discovery of three new substellar companions to solar-type stars, HD191806, HD214823, and HD221585, based on radial velocity measurements obtained at the Haute-Provence Observatory. Data from the SOPHIE spectrograph are combined with observations acquired with its predecessor, ELODIE, to detect and characterise the orbital parameters of three new gaseous giant and brown dwarf candidates. Additionally, we combine SOPHIE data with velocities obtained at the Lick Observatory to improve the parameters of an already known giant planet companion, HD16175 b. Thanks to the use of different instruments, the data sets of all four targets span more than ten years. Zero-point offsets between instruments are dealt with using Bayesian priors to incorporate the information we possess on the SOPHIE/ELODIE offset based on previous studies. The reported companions have orbital periods between three and five years and minimum masses between 1.6 Mjup and 19 Mjup. Additionally, we find that the star HD191806 is experiencing a secular acceleration of over 11 \ms\ per year, potentially due to an additional stellar or substellar companion. A search for the astrometric signature of these companions was carried out using Hipparcos data. No orbit was detected, but a significant upper limit to the companion mass can be set for HD221585, whose companion must be substellar. With the exception of HD191806 b, the companions are located within the habitable zone of their host star. Therefore, satellites orbiting these objects could be a propitious place for life to develop.

Investigating Dynamical Complexity of Geomagnetic Jerks Using Various Entropy Measures

Recently, many novel concepts originated in dynamical systems or information theory have been developed, partly motivated by specific research questions linked to geosciences, and found a variety of different applications. This continuously extending toolbox of nonlinear time series analysis highlights the importance of the dynamical complexity to understand the behavior of the complex Earth's system and its components. Here, we propose to apply such new approaches, mainly a series of entropy methods to the time series of the geomagnetic field. Two datasets provided by Chambon la Foret (France) and Niemegk (Germany) observatories are considered for analysis to detect dynamical complexity changes associated with geomagnetic jerks, the abrupt changes in the second temporal derivative of the Earth's magnetic field. The results clearly demonstrate the ability of Shannon and Tsallis entropies as well as Fisher information to detect events in a regional manner having identified complexities lower than the background in time intervals when geomagnetic jerks have already been reported in the literature. Additionally, these information measures are directly applicable to the original data without having to derive the secular variation or acceleration from the observatory monthly means. The strength of the proposed analysis to reveal dynamical complexity features associated with geomagnetic jerks can be utilized for analyzing not only ground measurements, but also satellite data, as those provided by the current magnetic field mission of Swarm.

Investigation of the SA evolution by using the CHAOS-4 model over 1997–2013

Abstract The temporal and spatial evolution characteristics of the geomagnetic secular acceleration (SA) are investigated, based on CHAOS-4 core field model during the period of 1997–2013. The SA evolution on a short time scale is associated with the phenomenon of the geomagnetic jerk. More details of the global extent and the occurrence time of the successive jerks (the 1999, 2003, 2007, and 2011 jerks) are obtained. The location, size and reversed polarity pattern for the 1999 jerk are similar to those for the 2003 jerk in the Asian-Indian sector. While the 2007 and 2011 jerks mainly take place in the Atlantic sector. The direction and speed of the shift for the four jerks are different, identified by the occurrence time of the jerks. The zonal motions of the SA patches exhibit an oscillation pattern in the Asian-Indian sector, whereas a purely westward drifting pattern is along the equator in the Atlantic sector. It is believed that the shift of the jerks is related to the motion of SA- B r patches observed at the core-mantle boundary (CMB).

Morphology of the southern African geomagnetic field derived from observatory and repeat station survey observations: 2005–2014

Geomagnetic field data from four observatories and annual field surveys between 2005 and 2015 provide a detailed description of Earth’s magnetic field changes over South Africa, Namibia and Botswana on time scales of less than 1 year. The southern African area is characterized by rapid changes in the secular variation pattern and lies in close proximity to the South Atlantic Anomaly (SAA) where the geomagnetic field intensity is almost 30 % weaker than in other regions at similar latitudes around the globe. Several geomagnetic secular acceleration (SA) pulses (geomagnetic jerks) around 2007, 2010 and 2012 could be identified over the last decade in southern Africa. We present a new regional field model for declination and horizontal and vertical intensity over southern Africa (Southern African REGional (SAREG)) which is based on field survey and observatory data and covering the time interval from 2005 to 2014, i.e. including the period between 2010 and 2013 when no low Earth-orbiting vector field satellite data are available. A comparative evaluation between SAREG and global field models like CHAOS-5, the CHAMP, Orsted and SAC-C model of the Earth's magnetic field and International Geomagnetic Reference Field (IGRF-12) reveals that a simple regional field model based on a relatively dense ground network is able to provide a realistic representation of the geomagnetic field in this area. We particularly note that a global field model like CHAOS-5 does not always indicate similar short-period patterns in the field components as revealed by observatory data, while representing the general secular variation reasonably well during the time interval without near-Earth satellite vector field data. This investigation further shows the inhomogeneous occurrence and distribution of secular variation impulses in the different geomagnetic field components and at different locations in southern African.

Time‐correlated patterns from spherical harmonic expansions: Application to geomagnetism

AbstractWe use empirical orthogonal function analysis (EOFA) directly on sets of Schmidt spherical harmonic (SH) coefficients modeling the internal geomagnetic field or its time derivatives at different epochs. We show how to properly use the method such that the application of EOFA to either spatial or spectral domains leads to the same results, bypassing the need to work on snapshots of field charts synthesized from SHs. In case a spatial grid is required, we point out which is the best grid to use. We apply the method to the CM4 geomagnetic field model to illustrate the differences in EOFA modes obtained with and without corrections. Once the corrected main modes of secular acceleration (SA) have been singled out, we retrieve previous results showing that the 1969, 1978, and 1991 geomagnetic field acceleration jumps have the same spatial pattern. A new finding in this study is that the same spatial pattern is present in principal modes of secular variation which, once inverted, may provide the flow responsible for the jerk sequence. Another finding is the unveiling of a different spatial structure common to a second group of jerks with SA pulses around 1985 and 1996, displaying a localization very similar to SA pulses identified in 2006 and 2009 using recent satellite data. Finally, if properly handled, the EOFA can be directly applied to a grid of data values of the geomagnetic field in order to produce SH models of decorrelated modes which may help to separate different sources of the field.

Evidence for a new geomagnetic jerk in 2014

AbstractThe production of quasi‐definitive data at Ebre observatory has enabled us to detect a new geomagnetic jerk in early 2014. This has been confirmed by analyzing data at several observatories in the European‐African and Western Pacific‐Australian sectors in the classical fashion of looking for the characteristic V shape of the geomagnetic secular variation trend. A global model produced with the latest available satellite and observatory data supports these findings, giving a global perspective on both the jerk and a related secular acceleration pulse at the core‐mantle boundary. We conclude that the jerk was most visible in the Atlantic and European sectors.

DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model

We present DTU’s candidate field models for IGRF-12 and the parent field model from which they were derived, CHAOS-5. Ten months of magnetic field observations from ESA’s Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. The internal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, compared with CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based on low-altitude CHAMP data, which was used in CHAOS-4. We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites: Orsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variation measured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarm magnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data are lower than those to Orsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5 shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013 pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.

A heuristic evaluation of long‐term global sea level acceleration

AbstractIn view of the scientific and social implications, the global mean sea level rise (GMSLR) and its possible causes and future trend have been a challenge for so long. For the twentieth century, reconstructions generally indicate a rate of GMSLR in the range of 1.5 to 2.0 mm yr−1. However, the existence of nonlinear trends is still debated, and current estimates of the secular acceleration are subject to ample uncertainties. Here we use various GMSLR estimates published on scholarly journals since the 1940s for a heuristic assessment of global sea level acceleration. The approach, alternative to sea level reconstructions, is based on simple statistical methods and exploits the principles of meta‐analysis. Our results point to a global sea level acceleration of 0.54 ± 0.27 mm/yr/century (1σ) between 1898 and 1975. This supports independent estimates and suggests that a sea level acceleration since the early 1900s is more likely than currently believed.

A candidate secular variation model for IGRF-12 based on Swarm data and inverse geodynamo modelling

In the context of the 12th release of the international geomagnetic reference field (IGRF), we present the methodology we followed to design a candidate secular variation model for years 2015–2020. An initial geomagnetic field model centered around 2014.3 is first constructed, based on Swarm magnetic measurements, for both the main field and its instantaneous secular variation. This initial model is next fed to an inverse geodynamo modelling framework in order to specify, for epoch 2014.3, the initial condition for the integration of a three-dimensional numerical dynamo model. The initialization phase combines the information contained in the initial model with that coming from the numerical dynamo model, in the form of three-dimensional multivariate statistics built from a numerical dynamo run unconstrained by data. We study the performance of this novel approach over two recent 5-year long intervals, 2005–2010 and 2009–2014. For a forecast horizon of 5 years, shorter than the large-scale secular acceleration time scale (∼10 years), we find that it is safer to neglect the flow acceleration and to assume that the flow determined by the initialization is steady. This steady flow is used to advance the three-dimensional induction equation forward in time, with the benefit of estimating the effects of magnetic diffusion. The result of this deterministic integration between 2015.0 and 2020.0 yields our candidate average secular variation model for that time frame, which is thus centered on 2017.5.

Fast equatorial waves propagating at the top of the Earth's core

AbstractSince 2000, magnetic field variations originating in the core have been dominated by several pulses in the secular acceleration, leading to sharp geomagnetic “jerks” at the Earth's surface. Using models built from (i) Defense Meteorological Satellite Program data and (ii) Ørsted and Swarm satellites and ground observatory data, we show that a new pulse occurred in 2012.5, immediately following two pulses in 2006 and 2009. The three pulses can be decomposed into several equatorially symmetric modes propagating eastward and westward at 550 to 1100 km/yr, and one equatorially antisymmetric mode propagating eastward at 1650 km/yr. The characteristics of these modes are compatible to some extent with equatorial magnetic Rossby waves propagating within a 140 km thick layer at the top of the core with a density contrast of 50 ppm. This interpretation, if confirmed, would provide a new explanation for geomagnetic jerks and pulses based on stable stratification of the core.

지역화된 동북아시아지역의 지구자기장 영년변화 모델: 1997-2011

동북아시아에 위치한 4개의 지자기 관측소의 3성분 지구자기장 관측 자료를 이용하여 1997년부터 2011년 동안의 지구자기장의 영년변화를 표현하는 지역화된 영년변화 모델을 제작하였다. 외핵의 움직임으로 발생되는 지구자기장은 장소와 시간에 따라 변화하며 지자기 관측소에서는 이를 시계열로 측정하게 된다. 따라서 공간적인 변화를 함께 파악하기 위해서는 이를 시공간모델로 제작하여 시간에 따른 지구자기장의 변화를 공간적으로도 표현할 수 있도록 해야 한다. 전지구 범위인 경우 관측소의 분포가 제한되어 있고 이를 공간적으로 보완하기 위해 위성 자료를 활용한다. 하지만 방대하고 복잡한 위성 자료의 처리와 세계의 모든 지자기 관측소의 자료를 활용하여 전 지구적 지구자기장의 모델을 제작하는 일은 상당한 작업과 노력을 요구한다. 또한 계속해서 들어오는 자료들을 이용하여 모델을 업데이트 하는 일 역시 같은 양의 시간과 노력을 필요로 하게 된다. 더불어, 각 관측소 자료의 오차범위와 위성 자료 처리 오차 (processing error) 역시 지역에 따라 다르게 나타남으로 이러한 오차값들이 전지구 모델의 정확도에 영향을 미칠 수 있다. 본 논문에서는 이러한 문제점을 감안하여 동북아시아 지역을 중심으로 하는 지역화된(localized) 모델링 기법을 소개하고 이를 통해 지구자기장의 영년변화 모델을 제작하는 데 적용하였다. 전 세계의 지구자기장 관측망인 INTERMAGNET에 가입된 3개의 일본 관측소와 1곳의 중국 관측소 자료를 활용하여 1997년부터 2011년까지 6개월 간격으로 지구자기장의 변화를 파악하고 이를 전지구 모델과 비교해 보았다. 또한 얻어진 모델을 이용하여 지구 내부의 원인인 지구자기장의 급작스런 변화를 일컫는 지구자기장 '급변'을 찾아보고 이에 대한 발생 시기에 대해 논의하였다. I produced a secular variation model of geomagnetic field by using the magnetic component data from four geomagnetic observatories located in Northeast Asia during the years between 1997 and 2011. The Earth's magnetic field varies with time and location due to the dynamics of fluid outer core and the magnetic observatories on the surface measure in time series. To adequately represent the magnetic field or secular variations of the Earth, a spatio-temporal model is required. In making a global model, satellite observations as well as limited observatory data are necessary to cover the regions and time intervals. However, you need a considerable work and time to process a huge amount of the dataset with complicated signal separation procedures. When you update the model, the same amount of chores is demanded. Besides, the global model might be affected by the measurement errors of each observatory that are biased and the processing errors in satellite data so that the accuracy of the model would be degraded. In this study, as considered these problems, I introduced a localized method in modeling secular variation of the Earth's magnetic field over Northeast Asia region. Secular variation data from three Japanese observatories and one Chinese observatory that are all in the INTERMAGNET are implemented in the model valid between 1997 to 2011 with the interval of 6 months. With the resulting model, I compared with the global model called CHAOS-4, which includes the main, secular variation and secular acceleration models between 1997 to 2013 by using the three satellites' databases and INTERMAGNET observatory data. Also, the geomagnetic 'jerk' which is known as a sudden change in the time derivatives of the main field of the Earth, was discussed from the localized secular acceleration coefficients derived from spline models.

An Investigation of the Secular Acceleration of Psychiatric Disorders

Secular acceleration, for example an increase in height in groups of people over a period of time of more than a century, is a unique, perhaps “ecological” event. In the study presented here, historical patient files from the Jena Psychiatric Clinic were evaluated in relation to the problem of acceleration. A first sampling of 119 patient files for the years 1880-1890 revealed that, for children and adolescents up until the end of their twentieth year of life, the average age at the time of their first admission was 17 years. Compared to this, the first admission of a second sample of 132 patient records for the years 1985-1987 revealed a clearly younger average age at first admission of 11 years. This difference in age was found to be statistically significant. The heights of 14-year-old subjects from the city of Jena for the years 1880 to 1975 obtained from the literature showed a documented increase in height of almost 20 cm. The results of our investigation revealed that, in addition to physical acceleration, there was also an advancement of pathological mental processes in the course of a period of 100 years.

Weight and height centiles of Argentinian children and adolescents: a comparison with WHO and national growth references

Background: Studies in several countries comparing the performance of WHO references and their own national growth standards reported differences that could affect screening and growth monitoring.Aim: To estimate weight and height centiles on a sample of Argentinian children and adolescents and compare selected centiles with WHO and national growth references.Subjects and methods: A cross-sectional school survey was conducted on 6239 boys and girls aged 5–18. Data were collected between 2005–2009 in Santa Rosa, Argentina. Smoothed weight and height centiles were estimated by the LMS method and compared with WHO 2007 and Argentinian (ARG) growth references.Results: Weight centiles were higher than those of WHO and ARG. Height centiles were above the ARG and below the WHO ones. The greatest differences with ARG were seen before puberty and then declined up to age 18. In contrast, differences with WHO increased from puberty onwards.Conclusion: Compared with the ARG reference, linear growth of these schoolchildren shows a secular acceleration without substantial improvements in the adult height. In relation to WHO, the results suggest that around the adolescent growth spurt differences in linear growth between populations became larger, limiting the clinical usefulness of international growth references in adolescents.

Geomagnetic secular acceleration, jerks, and a localized standing wave at the core surface from 2000 to 2010

The geomagnetic secular acceleration (SA), defined as the second‐order time derivative of the Earth's core magnetic field, is investigated using data from the CHAMP satellite. We present a set of SA spherical harmonic models calculated from 3 year time intervals of CHAMP data, centered on epochs ranging from 2002.19 to 2009.51 with a 30 day step. These models are parameterized as second‐order Taylor expansions in time and are not regularized, except for SA degrees larger than 8. We find that the SA underwent two power pulses in 2006 and 2009 at the core‐mantle boundary (mostly on degrees 5 and 6) and at the Earth's surface (mostly on degrees 2 to 4). These pulses take the form of intense SA patches at the core surface in the low‐latitude Atlantic sector and in the Indian Ocean sector. In the Atlantic sector, the 2006 and 2009 SA patches are markedly anticorrelated. Principal component analysis suggests that the two pulses are part of a standing wave of period about 6 years. At the Earth's surface, this wave results in a succession of geomagnetic jerks, i.e., sudden SA polarity changes, in 2003, 2007, and 2011 near the Atlantic sector. The 2011 jerk is detected using the latest observatory data available, including quasi‐definitive data from January to October 2013. The origin of the wave is not clear; we find that it cannot be generated by the zonal toroidal flow of a torsional oscillation. Other possible interpretations are discussed.

Toward a better representation of the secular variation. Case study: The European network of geomagnetic observatories

In the present paper we discuss a few issues regarding the secular variation (SV) and secular acceleration (SA) of the geomagnetic field that have consequences on mapping them at regional scales. Data from the European network of geomagnetic observatories have been analyzed from the perspective offered by existing long time series of annual means. The existence of high-frequency ingredients in the temporal change of the main field has been taken into account too. The importance of eliminating, from observatory and main field model data, prior to any discussion on secular variation, the signal related to external variations is demonstrated. Its consequences for SV analysis and/or mapping, including the jerk concept, are shown. Also, the importance of the geographical scale at which the SV is represented is discussed. To that aim, we used gufm1, IGRF and CM4 models for the main field from which the residual external signature was eliminated. The contribution of high-frequency ingredients to the map pattern is revealed. The results of the paper set additional observational constraints to the main field and geodynamo modeling.

PRECISE DOPPLER MONITORING OF BARNARD'S STAR

We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during 25 years between 1987 and 2012. The early precision was 20 \ms{} but was 2 \ms{} during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above $\sim$2 \ms{}, setting firm upper limits on the minimum mass (\msini) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 \mearth{} and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 \mearth{} (0.03 \mjup) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at $4.515\pm0.002$ \msy{}, consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity.